Virtue: The Prophet (peace and blessings of Allah be upon him) said: "Whoever wakes up at night and says: 'None has the right to be worshipped except Allah, alone and with no partner, to Him belongs [all] sovereignty and praise, and He is able to do all things; How far from imperfections Allah is, and all praise is for Allah, and none has the right to be worshipped except Allah, Allah is the greatest, and there is no power nor might except with Allah, The Most High, The Supreme.' and then supplicates: 'O my Lord forgive me.' will be forgiven." In another narration: "and then asks [for something], he will be answered. If he then performs ablution and prays, his prayer will be accepted."
Reference: Abu Dawud #5060