What is the meaning of the Prophet's (peace be upon him) saying: "No sin should reach him on that day except associating partners with Allah" or "No sin on that day will cling to him except associating partners with Allah"?

The Hadith was graded as hasan (good) by Al-Albani. The meaning of "and no sin should reach him on that day except associating partners with Allah" is that the one who recites this dhikr (remembrance) will not be completely destroyed by any sin in a way that nullifies his deeds, except for associating partners with Allah (shirk), for that indeed destroys him. So, if a servant supplicates with the word of Tawhid (monotheism), he has entered himself into a safe sanctuary. Thus, it is not befitting for a sin to violate Allah's sanctity. However, if he departs from the sanctity of Tawhid, shirk will inevitably reach him.