Sunan ad-Darimi

Ibn Abi Layla says: I met Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him), and he said: Shall I not give you a gift? The Messenger of Allah (peace and blessings be upon him) came to us, so we said: We have learned how to send peace upon you, but how should we send blessings (salat) upon you? He said: Say like this «(اللّٰهُمَّ صَلِّ عَلَىٰ مُحَمَّدٍ ...... إِنَّكَ حَمِيْدٌ مَجِيْدٌ)» "O Allah! Have mercy and grace upon Muhammad and the family of Muhammad as You had mercy and grace upon Ibrahim. Surely, You are Praiseworthy and Glorious. O Allah! Bless Muhammad and the family of Muhammad as You blessed Ibrahim. Surely, You are Praiseworthy and Glorious."

Naeem Mujmir narrates from the freed slave of Sayyiduna Umar bin Al-Khattab (may Allah be pleased with him) that Muhammad bin Abdullah bin Zaid Al-Ansari, who saw the dream of giving the Adhan during the time of the Messenger of Allah (peace and blessings be upon him) (the dream was seen by his father Abdullah as mentioned earlier and as in Muslim), informed that Sayyiduna Abu Mas’ud Al-Ansari Uqbah bin Amir (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) came to us and sat with us in the gathering of Sa’d bin Ubadah. Basheer bin Sa’d, who is Abu Nu’man bin Basheer, said to him: O Messenger of Allah! Allah Almighty has commanded us to send blessings upon you, so how should we send blessings upon you? He replied: “Say like this: «اللّٰهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَعَلىٰ آلِ مُحَمَّدٍ كَمَا صَلَّيْتَ عَلَى إِبْرَاهِيْمَ وَبَارِكْ عَلَى مُحَمَّدٍ وَعَلَى آلِ مُحَمَّدٍ كَمَا بَارَكْتَ عَلَى آلِ إِبْرَاهِيْمَ فِي الْعَالَمِيْنَ إِنَّكَ حَمِيْدٌ مَجِيْدٌ» and as for the way of greeting (salaam), you already know it.”