The Fiqh Learned on the Journey

Also, a lot of fiqh was learned during the ghazawāt. So this is another objective that was served by travelling with the Messenger of Allah (peace be upon him): they learned the fiqh from him. So during the ghazwah of Banū al-Muṣṭaliq, the ruling of tayammum was revealed in the Qur'an, and the fiqh of it was learned from the Messenger of Allah (peace be upon him) right then and there.

Also, another example, to show how they would learn fiqh in this ghazwah: in al-Bukhārī (4138), Abū Saʿīd al-Khudrī said, "We went forth with the Messenger of Allah on the expedition to Banū al-Muṣṭaliq. We took many of the Bedouin captive, and we desired the women, because celibacy was very hard on us. We liked the practice of ʿazl" — ʿazl is the interruption of sexual intercourse by the male's withdrawal before ejaculation, so we can say that it's a form of contraceptive. So he says, "We liked the practice of ʿazl, but wondered whether we should do this without asking the Messenger of Allah. So we asked him about it. He said, 'There is no difference in you doing that, for any soul that is going to exist till Judgement Day will so exist.'" So the Messenger of Allah (peace be upon him) said that it wouldn't make a difference if you do that or not, because Allah has already made qadar — has already ordained — every soul that will be created.

Now, some ʿulamāʾ use this ḥadīth as evidence that contraceptives are allowed. The fiqh of it is not gone into here: among our classical scholars, for example, there is a difference of opinion on whether it is mubāḥ or makrūh or ḥarām; and then there's also a difference of opinion on whether this is relating to a free woman, a wife, or a slave girl. Now, the reason why they wanted to practise ʿazl here appears in the narration of this ḥadīth in Ṣaḥīḥ Muslim (1438), where Abū Saʿīd says that they also desired ransom for the captives. It is because if a man owns a slave woman and she becomes pregnant and has a child from him, then he cannot sell her. So she remains with him now because of the children, and she is called umm walad, a mother of children, and she becomes almost like his wife. However, if they are practising ʿazl, then they would have relations with these women, but then they can sell them. So that's why they were asking the Messenger of Allah (peace be upon him) about it.