What is meant by the scholars' saying that whoever insults Allah, his repentance is accepted because Allah is transcendent, but whoever insults the Messenger, his repentance is not accepted because he is a human being subject to imperfection?

The Muslim ruler executes whoever insults Allah Almighty or His Messenger, peace and blessings be upon him, or any of the prophets, and he is not asked to repent, unlike the apostate. As for the repentance of one who insults the Messenger, peace and blessings be upon him, the scholarly dispute revolves around whether repentance exempts him from execution, not around whether his repentance benefits him with Allah in the hereafter. A sincere repentance erases what came before it.