Abu Huraira said that God’s Messenger used to commend prayer at night in Ramadan, but did not command it as a duty. He would say, “If anyone prays during the night in Ramadan because of faith and seeking his reward from God, his former sins will be forgiven him.” When God’s Messenger died this was the practice, and it continued thus during Abu Bakr’s Caliphate and the early part of ‘Umar’s. Muslim transmitted it.