First: He is the Lord of all worlds. It would not be fitting for Him to leave His servants neglected and without guidance, without teaching them what benefits them in their worldly life and their life to come, and what harms them in both. This would diminish His lordship and attribute to the Lord Most High what does not befit Him. Whoever attributes this to Him has not esteemed Him as He deserves.
Second: This follows from the name “Allah,” meaning the One who is worshipped. His servants have no way of knowing how to worship Him except through His messengers.
The third indication comes from His name “the Most Compassionate.” His mercy precludes neglecting His servants and failing to teach them how to attain their fullest perfection. Whoever gives the name “the Most Compassionate” its due recognizes that it implies the sending of messengers and the revelation of scriptures far more strongly than it implies knowledge of the sending down of rain «1», the growth of herbage «2», and the bringing forth of grain. Mercy calls for what gives life to hearts and souls more strongly than it calls for what gives life to physical bodies. Yet those whose understanding is veiled perceive in this name only the share enjoyed by livestock and other creatures «3», whereas people of understanding perceive something beyond that.
The fourth indication comes from the mention of the “Day of Judgment.” This is the day when Allah will recompense His servants for their deeds, rewarding them for good deeds and punishing them for acts of disobedience and wrongdoing. Allah would never punish anyone before establishing the proof against them, and that proof is established only through His messengers and His scriptures.
Through the messengers, reward and punishment become deserved. Through them, the affairs of the Day of Judgment are set in motion, and the righteous are led to bliss and the wicked to Hell.
The fifth indication comes from His words, “You alone we worship.” The acts by which He, Most High, is worshipped must accord with what He loves and approves. Worshipping Him—thanking Him, loving Him, and fearing Him—is innate and intelligible to sound minds. Yet there is no way to know the manner of worship, or the acts by which He is worshipped, except through His messengers. This makes clear that the sending of messengers is firmly established in reason, and that it is impossible