Rabbi Elazar said, “Whoever divorces his first wife, even the Altar sheds tears for him.” After the mishna on amud alef teaches the rulings of Beit Shammai, Beit Hillel and Rabbi Akiva regarding what constitutes “grounds for divorce”, based on how to interpret the verse in the Chumash regarding an acceptable reason to permit divorce (Duet. 24:1), Rabbi Elazer cites an additional source that discourages divorce if at all possible. He quotes a prophecy of Malachi, “And this second thing you do, to cover the Altar of the G-d with tears, weeping, and sighing, such that He will no longer turn to the offering, nor will He take anything willingly from your hand. And you will say, ‘Why?’ Because the G-d testified between you and the wife of your youth, that you dealt treacherously with her, and she is your companion and the wife of your covenant.” (Malachi 2:13-14)
Based on these verses Rabbi Elazar teaches, “Whoever divorces his first wife, even the Altar sheds tears for him.” This may sound like merely a poignant idea but not a legal issue, especially since nowadays we are without merit of having a Beit Hamikdash with an actual Altar. However, his teaching is in fact cited as halacha in the Shulchan Aruch, Even Ha’Ezer 119:3. The Rema cites Rabbi Elazar’s teaching as reason to forbid divorce even in a situation where it is permitted, providing the wife was not unfaithful (in which case it would be a mitzvah to divorce), or unless the woman also wants to divorce. The Mechaber states that one should “not hurry” to divorce (unless required by halacha), based on this same teaching of Rabbi Elazar.