I would like to know the difference between
salla allah alayhi wa salam,
which we use for the prophet Muhammad and
aleyhi salam,
which we use for all the other prophets. Why don't we use a single formula for all the prophets?
The salutation صلى الله عليه وسلم can be used with any other prophet. Apparently classical scholars didn't make this distinction. For example, ibn Jarir al-Tabari (d. 310 AH) in his exegesis uses this salutation for:
لأن هوداً صلى الله عليه وسلم إنـما دعا قومه إلـى توحيد الله لـيغفر لهم ذنوبهم
قال إبراهيـم صلى الله عليه وسلم: فإن الله الذي هو ربـي يأتـي بـالشمس من مشرقها
أمر الله بنـي إسرائيـل أن يسيروا إلـى الأرض الـمقدّسة مع نبـيهم موسى صلى الله عليه وسلم فلـما كانوا قريبـاً من الـمدينة
Muhammad Rasulullah was given special gift from Allah, shalawat. Allah and angels give shalawat to Muhammad.
We as the ummah also strongly command to give sholawat too.
so that’s why, when we say Muhammad, we say Salla Allahu `alayhi wa salam.
And the other prophet as sunnah teach, we should only say `alayhi salam.