كتاب النكاح : Hadeeth No:4743 : 'Abdullah:
We used to participate in the holy battles led by Allah's Apostle and
we had nothing (no wives) with us. So we said, "Shall we get ourselves
castrated?" He forbade us that and then allowed us to marry women with
a temporary contract (2) and recited to us: -- 'O you who believe !