Ibn ‘Umar reported God’s Messenger as saying, “Prayer during the night should consist of pairs of rak'as, but if one of you fears the morning is near he should pray one rak'a which will make his prayer an odd number for him.”
‘A’isha said that God’s Messenger used to pray thirteen rak'as during the night, observing a witr out of that with five, and sitting only during the last of them.
Salim b. Abul Ja'd told of a man of Khuza'a saying, “I wish I had prayed and been at rest.” When the people seemed to disapprove of his saying that, he replied that he had heard God’s Messenger say, “Declare that the time for prayer has come, Bilal, and give us rest by it.”*
* This probably means that prayer brings peace of mind.