Mukhtasar Muslim

Abu Huraira (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings of Allah be upon him) used to encourage the offering of Tarawih prayers in Ramadan, but did not make it obligatory. He said: Whoever prays during Ramadan with faith and seeking reward, his previous sins will be forgiven. Then the Messenger of Allah (peace and blessings of Allah be upon him) passed away and the matter remained as it was. The same practice continued during the caliphate of Abu Bakr (may Allah be pleased with him). And in the early period of the caliphate of Umar (may Allah be pleased with him), the same method remained (i.e., whoever wished would pray at night).