Abu Umama told of his hearing God’s Messenger say, “If anyone goes to bed in a state of purity and makes mention of God till drowsiness overtakes him, he will not turn round at any time during the night and ask God at that time for some of the good of this world and the next without His giving it to him.”
Nawawi mentioned it in Kitab al-adhkar by the transmission of Ibn as-Sunni.