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.
He said he asked the Prophet about a man who prays sitting, and he replied, “If he prays standing that is more excellent; but one who prays sitting has half the reward of one who stands, and one who prays lying down has half the reward of one who sits.”
Narrated ‘Abdallah b. Mas'ud reported God’s Messenger as saying:
Our Lord is pleased with two men. One is a man who gets up from his blanket and his covering from among his beloved and his family to engage in prayer. God says to His angels, “Look at my servant who has got up from his bedding and his blanket from among his beloved and his family to engage in his prayer out of desire for what is with me and fear of what is with me.” The other is a man who goes out on an expedition in God’s path and is routed along with his companions, but who, knowing what responsibility will rest upon him for being routed and what reward he will receive for going back, returns with the result that his blood is spilt. God says to His angels, “Look at my servant who returned out of desire for what is with me and fear of what is with me with the result that his blood was spilt.”
‘Imran b. Husain reported God’s Messenger as saying, “Pray standing, but if you are unable, do it sitting; and if you are unable to do that, do it lying on your side.”