(Background: The Rebbe is discussing the opinion of Rabbi Meir of Rothenburg, based on the Jerusalem Talmud, that nowadays a wife cannot force her husband to move to Eretz Yisroel. The Chasam Sofer argues that our Babylonian Talmud, and thus normative halacha, does not follow Rabbi Meir of Rothenburg, since we see that the law that a slave wishing to go to Eretz Yisroel can indeed force his master to free him even nowadays. However, the Rebbe in Siman 2 drew a distinction between slave and wife: the law to free a slave is an explicit verse in the Torah whose reason we do not know, while the law of the wife forcing her husband is a Rabbinic enactment to encourage people to move to Eretz Yisroel.)
The Korban Nesanel also agrees with this distinction between the wife and the slave. For in his commentary on the Rosh at the end of Kesubos and in Gittin (Chapter 4, siman 43) he quotes the Rambam and Tur, who say that the law of the slave applies even in today’s times, when Eretz Yisroel is in gentile hands. The Korban Nesanel comments that this is true even according to Tosafos and Rabbi Meir of Rothenberg, who say that nowadays a wife cannot force her husband to move to Eretz Yisroel. It seems that the Korban Nesanel found evidence to this in the words of the Tur himself. For otherwise why did the Tur have to state specifically that the law applies nowadays? Aren’t all the laws of the Tur written for our time? The Tur omits from his code all the laws in the Talmud that applied only in Temple times. Only the Rambam, who brings even laws that do not apply today, had to specify that this particular law does not apply nowadays, but why did the Tur have to say this? The answer must be that the Tur means that although the law of the wife has changed according to Tosafos and Rabbi Meir of Rothenberg, the law of the slave has not changed.
In any case, we see that the Korban Nesanel agrees with my argument according to the Beis Shmuel, that there is a distinction between the wife and the slave.
However, the reason that the Korban Nesanel gives to explain the difference between wife and slave is hard to understand. He says, “A wife cannot force her husband because we must take into account the dangers of travel and the limited possibilities of earning a livelihood in Eretz Yisroel; this does not apply to the slave, since he has already run away." This implies that the Rambam and Tur hold that a slave may force his master to move to Eretz Yisroel or else free him only if the slave has already run away. But actually, they state the law even regarding a slave who has not yet run away but wishes to move to Eretz Yisroel. This is explicit in the Tur, Beis Yosef and Shulchan Aruch Yoreh Deah 267:84: that if a slave wishes to move to Eretz Yisroel, the master must either go with him, or sell him to someone moving there, or free him. It doesn't mention a word about a slave who has already run away. (That is dealt with in the next paragraph, 85.) And the Shulchan Aruch writes that this law applies even nowadays.
Also, it's hard to understand why the fact that the slave has run away should make any difference. (Although the slave has already overcome the obstacles of dangerous travel and earning a livelihood in Eretz Yisroel, the master has not, so why should the slave be allowed to force his master any more than a wife can force her husband?)
However, the Korban Nesanel says to look at the Bach, and from the Bach we can understand the difference between the wife and the slave. The Tur in Even Hoezer 75 quotes Rabbi Meir of Rothenberg (that only husband can force wife and not vice versa) and asks, if the Jerusalem Talmud, which says this, is talking nowadays when there is no mitzvah to move to Eretz Yisroel, then how can the husband force the wife? And on this the Bach replies that really there is a mitzvah even nowadays, but the difference is that in Temple times there was a good economy in Eretz Yisroel and it was easy to make a living, whereas nowadays it is difficult. Therefore, since the husband has the responsibility to earn a living and support her, she cannot force him to move to a place where he fears he may have trouble doing so, but he can force her to move if he feels confident he will be able to earn a living there.
Of course, the poskim (who rule in accordance with Rabbi Meir of Rothenberg) write this rule that the wife cannot force him in all cases; they make no exceptions for cases when the husband is very wealthy (and does not need to worry about making a living anywhere), or cases where he knows he has a good business in Eretz Yisroel but still does not wish to move there. (The reason is because one never knows what is to come. Wealthy people may one day become poor.) This is especially true according to the Me'il Tzedaka Siman 26, quoted in the Pischei Teshuva Siman 75, who despite being one of those who holds completely like the Ramban's opinion that living in Eretz Yisroel is a Torah mitzvah even nowadays - see the responsum where he writes at length to refute all the opinions that disagree with the Ramban, including Rabbeinu Chaim in Tosafos Kesubos 110b, and concludes that it is obligatory to go to Eretz Yisroel even if one has small children - says that there is one condition: that one must have a plentiful source of income in Eretz Yisroel, because if not, poverty can, G-d forbid, cause a person to go against his own best judgment and the will of Hashem (Eiruvin 41b). And even if he is sure of himself that he will able to tolerate a life of deprivation to serve Hashem there, he has no right to bring his little children into this lifestyle, for it is harming them - perhaps they won't be able to withstand the trial and will go off the path of Torah, G-d forbid. And those who leave behind their jobs in the Diaspora and move to Eretz Yisroel, where they will have to live off charity, are not doing the right thing, because someone who lives off his own work is greater than one who fears Heaven (Berachos 8b). The Chasam Sofer in his responsa, Even Hoezer v. 1 siman 132, writes that the Me'il Tzedaka's words are sweet to the palate, and he rules that the halacha is like him.
(One might argue that the Old Yishuv Jews who lived off chalukah, charity from abroad, must have disagreed with the Me'il Tzedaka, because they left behind their jobs in Europe to go and live off charity in Eretz Yisroel. But the truth is that they went there not just to fulfill the mitzvah of living in Eretz Yisroel; they went to learn Torah and serve Hashem. The Me'il Tzedaka only stated that the mitzvah of living in Eretz Yisroel is outweighed by the advantage of living off one's own work.)
So certainly according to the many authorities who hold that there is no mitzvah at all to go to Eretz Yisroel nowadays, as will be explained at length in the second Maamar which I plan to write, G-d willing, to explain all the different opinions in the Talmud and Poskim regarding the mitzvah of living in Eretz Yisroel, one should not go if he is not sure he will have income there. But even the Me'il Tzedaka, who is among those who hold it is a great obligation to move to Eretz Yisroel even nowadays - even he says that this is only if he is sure he will have plentiful income there. So all agree that there is no obligation to go to Eretz Yisroel if he is not sure he will have income there. Now, it is uncertain whether the law of a husband forcing a wife would still apply if the husband wants to go to Eretz Yisroel despite the fact that he is not sure he will have income there. Elsewhere I will speak about this, G-d willing. But in any case, it is clear that the Bach's logic for why the wife cannot force him nowadays applies even if he does have income there, or he is very wealthy and will not have to worry about income, for wealth is a "wheel that turns in the world" - the wealthy may one day become poor. So the rabbinic law makes no distinctions, since poverty is common there, and so when the wife demands that they move to Eretz Yisroel, the husband can respond that he is afraid he may become poor and have no income there. But the wife has no responsibility to bring in income; only the husband has to do whatever is necessary to support his wife.
According to the above, we understand well the difference between a wife and a slave. The Mishnah in Gittin 11b says that a master is not obligated to support his slave, and so the Shulchan Aruch rules in Yoreh Deah 267. Therefore, a wife cannot force her husband to move to Eretz Yisroel, because we suspect that she takes the income issue lightly since she is not responsible for income, and he has the right to say no. But a slave will not take income lightly, since if the going gets tough the master does not have to support him, and he will have to take care of himself. Therefore it is unusual that he would try to force his master to move to a place where it will be difficult for both of them to earn a livelihood, and that is why the Sages granted the slave the same rights as the master in moving to Eretz Yisroel. And now we understand the distinction made by the Korban Nesanel and the Beis Shmuel (although this is not the Korban Nesanel's own answer - he says the slave is different because he has already run away, and we still don't have an explanation for that).
However, it is still puzzling why the Korban Nesanel implies that the Tur would agree with his distinction - doesn't the Tur reject the opinion of Rabbi Meir of Rothenberg, that the wife has no right to force the husband? So clearly the Tur did not want to say the Bach's answer that the wife has no responsbility to bring in the income. But perhaps the Tur did not completely reject Rabbi Meir; he only writes that Rabbi Meir's explanation is "not sufficient" which implies that he recognizes the idea of the answer, perhaps with the Bach's explanation, only holds that it's not sufficient. Thus when he write that the law of a slave forcing applies even today, perhaps he means even according to Rabbi Meir, as the Korban Nesanel says, although he himself does not agree with Rabbi Meir. After all, it is common in the Mishnah and Gemara for one side of a dispute to make a statement unequivocally, yet later it emerges that he himself did not agree with the statement and he said it only according to his opponent's line of reasoning.