Sayyiduna Samurah (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) ordered us that when we are in the middle of the prayer, or at the time of its conclusion, (he said:) before the salam begin by saying: "All verbal worship, all pure words, all prayers (acts of bodily worship), peace and dominion belong to Allah alone"; then send salam upon the prophets, then send salam upon your near relatives and upon yourselves.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6988