Why did the Messenger, may God bless him and grant him peace, distance himself from saj‘ (rhymed prose), while the Holy Qur’an is full of it?

The Prophet, peace and blessings be upon him, and his companions disliked contrived saj' (rhymed prose) in sermons and supplications, out of caution against resembling soothsayers and against prohibited artificiality. However, they would use non-contrived saj' due to its beauty and harmony. The blameworthy saj' is the contrived type that diminishes humility and distracts from supplication, whereas what comes without contrivance is good.

As for the presence of saj' in the Holy Quran, scholars have differed on this matter. Some of them believe that there is no saj' in it, but rather there are "fawasil" (chapter-ending rhyming words/phrases).