Ubayy b. Ka'b said he told God’s Messenger that he frequently invoked blessings on him and asked how much of his prayer* he should devote to him. He replied that he might devote as much as he wished, and when he suggested a quarter he said,“Whatever you wish, but if you increase it that will be better for you.”He suggested a half and he replied,“Whatever you wish, but if you increase it that will be better for you.”He suggested two-thirds and he replied,“Whatever you wish, but if you increase it that will be better for you.”He then suggested devoting all his prayer to him and he replied,“Then you will be freed from care and your sin will be expiated.”* The word used is salat. It has been explained as referring here to the petitions (du’a) offered at the end of the salat. Tirmidhi transmitted it.