How sound and what is the meaning of the Hadith: "I sought permission from my Lord to visit my mother's grave, and He permitted me; and I sought His permission to pray for her forgiveness, but He did not permit me"?

The aforementioned hadith is authentic, narrated by Muslim, and its wording states that the Prophet, peace and blessings be upon him, visited his mother's grave, and he wept, and caused those around him to weep, clarifying that he sought permission from his Lord to ask for forgiveness for her, but he was not granted permission. He then sought permission to visit her grave, and he was granted permission. He commanded visiting graves because they remind one of death. Al-Nawawi mentioned that the reason for his visit to his mother's grave was the profound admonition and remembrance it offered, and his command to visit graves supports this. The hadith indicates the permissibility of visiting the graves of non-Muslims, and the prohibition of seeking forgiveness for them.