Both commentators, despite not classifying the splitting of the moon as one of the miracles of the Prophet, acknowledge that this event emphasizes the truth of the Prophethood and Messengership of the Messenger of Allah, and supports his warning and invitation.
Maulana Islahi has written:
We have referred multiple times in this book to a practice of Allah Almighty, that although signs of His power and wisdom are present throughout every inch of the heavens and the earth, and new signs continue to become manifest day by day, during the time of the messenger’s missions, Allah Almighty specifically reveals such signs through which the warnings of the messenger and the truthfulness of his claim to messengership become evident. This divine practice is mentioned throughout the Qur’an. We present one verse as an example. Allah has stated: ‘We shall also show them Our signs in the world around them and within them as well’
The purpose of these signs, as we have indicated, is to reinforce the warning of the Messenger. The messages that the Messenger proclaims through words are supported by evidence and signs that appear in this universe in various forms so that God’s argument is completely evident upon the people. A similar sign was manifested in the form of the splitting of the moon to support the warning of the Messenger of Allah (PBUH), so that it would be clearly evident to the deniers of punishment and resurrection that the Qur’an’s warnings about the Day when the earth will be shaken, mountains will become dust and scatter in the atmosphere, seas will boil over, and the sun will become darkened are not just to intimidate them, but these are truths that will inevitably occur one day. These are not impossible events; their indications manifest in this world in one form or another. (Tadabbur-e- Qur’an 8/90-91)
Maulana Maududi states:
This was indeed a prominent proof of the truthfulness of the Prophet, as the event was confirming the news about the Day of Judgment that he had given to the people. (Tafheem-ul-Qur’an 5/230)