The Messenger of Allah (blessings and peace of Allah be upon him) said: “May his nose be robbed in the dust, one in whose presence I am mentioned and he does not send blessings upon me.” Narrated and classed as hasan by at-Tirmidhi (3545); classed as saheeh by al-Albaani in Saheeh Sunan at-Tirmidhi.
It was narrated from al-Husayn ibn ‘Ali ibn Abi Taalib (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: “The miser is the one in whose presence I am mentioned and he does not send blessings upon me.” Narrated and classed as hasan by at-Tirmidhi (3546); classed as saheeh by al-Albaani in Saheeh Sunan at-Tirmidhi.
Al-Faakihaani (may Allah have mercy on him) said:
The hadith “The miser is the one in whose presence I am mentioned and he does not send blessings upon me” supports the view of those who say that it is obligatory to send blessings upon him every time he is mentioned, and this is the view towards which I am inclined.
End quote from al-Qawl al-Badee‘ fi’s-Salaah ‘ala al-Habeeb ash-Shafee‘ (p. 31)
This is also the view of a number of scholars, including: at-Tahhaawi among the Hanafis; at-Tartooshi and Ibn al-‘Arabi among the Maalikis; Abu ‘Abdullah al-Haleemi and Abu Haamid al-Isfaraayeeni among the Shaafa‘is; and Ibn Battah among the Hanbalis.
Al-Mawsoo‘ah al-Fiqhiyyah (1/204).