What is the ruling on saying "Salat al-Nabi" (Prayer upon the Prophet) upon completing a task, as an indication of its completion?

Scholars have differed on the ruling of invoking blessings upon the Prophet, peace and blessings be upon him, for a worldly purpose, such as signaling the completion of a task. Some have permitted it, some have deemed it disliked, and some have forbidden it.

Some Shafi'is have held that it is not disliked to invoke blessings upon the Prophet, peace and blessings be upon him, when expressing astonishment. However, they disliked invoking blessings upon him when encountering something repulsive. Some Hanafis have forbidden invoking blessings upon the Prophet, peace and blessings be upon him, when performing a forbidden act or displaying merchandise.

Some Malikis disliked invoking blessings upon the Prophet, peace and blessings be upon him, when expressing astonishment, and they said: "Blessings should not be invoked upon him except when seeking reward and recompense."

Some Hanafis view it as disliked to invoke blessings upon the Prophet, peace and blessings be upon him, with the intention of informing people that a lesson has concluded.

Therefore, a Muslim should not make invoking blessings upon the Prophet, peace and blessings be upon him, a sign of completing tasks without the intention of worshiping through it, in order to avoid disagreement.