What is the meaning of "He will let down His covering upon him" mentioned in the noble Hadith that speaks of a servant drawing near to his Lord on the Day of Resurrection and Him concealing his sins?

The meaning of "yadha‘u kanafahu" (places His wing/cover) is to conceal him. Al-Nawawi and Ibn Hajar explained this, pointing out that "al-kanaf" (the wing/cover) is a covering, and that the meaning is to encompass the person with complete care.