Droplets from the ocean of Knowledge of the prophet

A note

There are innumerable things that make our Lord known to us. The three greatest and most universal are:
The first is this universe, some signs of which [concerning the existence and Unity of our Lord] you have already heard.
The second is the Seal of the Prophets, upon him be peace and blessings. He is the greatest of our Lord's signs in the universe and the key to His hidden treasures.
The third is the holy Qur'an, which is the interpreter of the book of the universe and God's argument against creatures.
Surely, we should recognize the second sign, the Prophet Muhammad, upon him be peace and blessings, who is an articulate, indisputable "argument" [for our Lord], and then listen to what he says. From the ocean of knowledge of that sign, we shall mention a few droplets.