Did the Prophet (peace be upon him) maintain four rak'ahs before and after Dhuhr, which are said to grant salvation from the Fire?

It has been authentically reported from the Prophet (peace be upon him) that "whoever prays four rak'ahs before Dhuhr and four after it, the Fire shall not touch him." And the Prophet (peace be upon him) never used to abandon four rak'ahs before Dhuhr. There is no hadith that proves his continuous performance of four rak'ahs after Dhuhr, but its indication of good is sufficient. The Prophet (peace be upon him) might have abstained from some virtuous deeds fearing that they might become obligatory upon his Ummah or out of dislike for burdening them.