What is the ruling on insulting the Prophet, peace be upon him, or disparaging him? Is it considered disbelief? And what is the interpretation of the Hadith about the man who said to the Prophet, "Be just, O Muhammad"?

This Hadith is narrated by the two Sheikhs from Abu Sa'id Al-Khudri that Ali ibn Abi Talib sent a small amount of gold from Yemen to the Prophet, peace be upon him. The Prophet, peace be upon him, divided it among four men. A man objected and said: "We were more deserving of this." When this reached the Prophet, peace be upon him, he said: "Will you not trust me, while I am the trustee of Him who is in the heavens?" Then a man with sunken eyes, a bushy beard, a shaven head, and a tucked-up garment stood up and said: "O Messenger of Allah, fear Allah!" The Prophet, peace be upon him, said: "Woe to you! Am I not the most deserving among the people of the earth to fear Allah?!" The man turned away, and Khalid ibn Al-Walid said: "Shall I not strike his neck?" He replied: "No, perhaps he performs Salah." Khalid said: "How many a performer of Salah says with his tongue what is not in his heart?!" The Messenger of Allah, peace be upon him, said: "I have not been commanded to delve into the hearts of people, nor to cut open their bellies." Then he looked at him as he was turning away and said: "Indeed, from the lineage of this man will emerge a people who recite the Book of Allah freshly, but it will not go beyond their throats. They will pass out of the religion as an arrow passes through its target. If I live to see them, I will kill them with the killing of Thamud."

Sheikh al-Islam Ibn Taymiyyah mentioned that the Prophet, peace be upon him, commanded the killing of those who were of the same type as this man who slandered him, and he informed that they are the worst of creation and that they are among the hypocrites. However, the Prophet, peace be upon him, forbade his killing for several reasons: either because he performed Salah, or so that people would not say that Muhammad kills his companions, or because he knew that he had companions who would emerge later. Scholars have unanimously agreed that slandering the Prophet, peace be upon him, is disbelief that expels one from the religion. Dhul-Khuwaisirah was not a companion; rather, he is counted among the hypocrites.