Sheikh `Abd al-Rahmân al-Barrâk
The Prophet (peace be upon him) said: “May Allah’s peace and blessing be upon Al Abî Awfâ.” [Sahîh al-Bukhârî]
Al Abî Awfâ was the name of a particular clan.
From this hadîth, we can derive the permissibility of saying “peace be upon him” when speaking about people who were not prophets or messengers. However, it should not be used habitually for anyone who was not a prophet. It should only be practiced all the time for the Prophets (peace be upon them).
And Allah knows best.
Source: Islam Today