Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "When you send blessings upon the Messenger of Allah (peace and blessings be upon him), send blessings upon him in a beautiful way, for you do not know; perhaps it will be presented to him (peace and blessings be upon him)." The narrator said: Then he taught us; he said: "Say: 'O Allah, send Your blessings, Your mercy and Your bounties upon the leader of the Messengers, the imam of the God-fearing and the Seal of the Prophets, Muhammad (peace and blessings be upon him), Your servant and Your Messenger, the imam of goodness, the guide to goodness and the Messenger of mercy. O Allah, raise him to the Praised Station (al-Maqam al-Mahmud), for which the first and the last will envy him. O Allah, send blessings upon Muhammad (peace and blessings be upon him) and upon the family of Muhammad, as You sent blessings upon Ibrahim (peace be upon him) and the family of Ibrahim; indeed You are Praiseworthy, Glorious.'"
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8562