It was narrated that Ibn Abi Laila said

"Ka'b bin Ujrah said to me: 'Shall I not give you a gift?' We said: "O Messenger of Allah (ﷺ), we know about sending salams upon you, but how should we send salah upon you?" He said: 'Say: Alahumma salli 'ala Muhammad wa 'ala ali Muhammad, kama sallaita 'ala Ibrahima wa barik 'ala Muhammad kama barakta 'ala ali Ibrahim fil-'alamin, innaka hamidun majid (O Allah, send salah upon Muhammad and upon the family of Muhammad, as You sent salah upon the family of Ibrahim, and send blessings upon Muhammad and upon the family of Muhammad as You sent blessings upon the family of Ibrahim among the nations. You are indeed Worthy of praise, Full of glory.)'"