He may believe in the messenger of God...

He may believe in the messenger of God, but he may not believe in what has been revealed to him. He may believe in the messenger of God, but not in his successors, or may not believe in the hereafter. The pious are those who have all kinds of belief, which we have just mentioned, in their minds and hearts.

As for the word “belief”, Imam Reza (AS) has narrated from the Messenger of Allah (SAW) his saying: “Belief is knowledge in the heart, acknowledgement with the tongue, and action with the organs of the body.”[^15] Abu as-Salt al-Harawi says: “I asked Imam Reza (AS) about the meaning of belief, and he said: ‘Belief is faith in the heart, declaring it with the tongue, and acting with the organs of the body.”[^16] Imam Ali (AS) said: “I asked the Messenger of Allah (SAW) about the meaning of belief, and he said: ‘Belief is what we accept in the heart, say it with the tongue, and act with the organs…