Sunan An-Nasa'i

Narrated 'Alqamah:It was narrated from 'Alqamah and Al-Aswad that 'Abdullah said: ""The Messenger of Allah said to us: 'Whoever among you can afford it, let him get married, and whoever cannot then he should fast, for it will be a restraint (wija') for him.'"" Abu Abdur-Rahman said: (The mention of) Al-Aswad in this hadith is not preserved