What is the meaning of the Hadith, "There is no Muslim who sends salutations upon me except that Allah returns my soul to me so that I may return his salutation," and does it mean that the Prophet's soul (peace and blessings be upon him) remains with him permanently to return salutations to those who send them, and how do we reconcile this Hadith with the Hadith, "The Prophets are alive in their graves, praying"?

There is no hadith stating that the soul of the Prophet, peace and blessings be upon him, is returned to him when one sends blessings upon him. The hadith that has been narrated is: "There is no one who sends salutations upon me except that Allah returns my soul to me so that I may return his salutation." Scholars have mentioned several interpretations for the hadith of the soul's return. Among them are: that the soul's return occurred previously, immediately after his burial; or that it is not a withdrawal of death; or that what is meant by "soul" is the angel entrusted with that task; or that what is meant by it is speech; or that he is absorbed in the affairs of the Higher Assembly, and when salutations are sent upon him, his comprehension returns to him so he can respond. The hadith "The prophets are alive in their graves, praying" has been authenticated, and it can be reconciled with the hadith of the soul's return through the aforementioned interpretations.