Musnad Abu Ya'la al-Mawsili 152:314

Abu Khaythama narrated to us, Marwan bin Mu'awiyah al-Fazari narrated to us, from Isma'il bin Abi Khalid, from Qays bin Abi Hazim, who said: I heard Abdullah bin Mas'ud saying: We used to go on military expeditions with the Messenger of Allah (peace and blessings of Allah be upon him) while we had no women with us. So we said: "O Messenger of Allah, shall we castrate ourselves?" He forbade us from that and commanded us to marry a woman for a garment. Then Abdullah recited: "O you who have believed, do not prohibit the good things which Allah has made lawful to you."