ما هو أصل عبارة "وصحبه وسلم" في قول "قال رسول الله صلى الله عليه وآله وصحبه وسلم"؟

Scholars have differed regarding the permissibility of invoking blessings upon others besides the Prophet (peace be upon him). Some have permitted it dependently, while others have permitted it independently. It has been narrated from Imam Ahmad that it is permissible to invoke blessings upon others besides the Prophet (peace be upon him) independently, citing as evidence Ali's saying to Umar: "May Allah bless you." There is nothing to prevent invoking blessings upon his family and companions dependently, and indeed, the writings of early and later scholars are rarely devoid of this expression.