Ibrahim bin Sa'd bin Ibrahim إبراهيم بن سعد بن إبراهيم · The Book of Fasting

A similar, Mursal, report was narrated from 'Ikramah.

the Messenger of Allah used to encourage the people to pray Qiyam in Ramadan, without insisting on that. He said: "Whoever spends the nights of Ramadan in prayer out of faith and in the hope of reward, he will be forgiven his previous sins." '