First essential:

The Prophet's every act and state bears witness to his Prophethood and faithfulness. But not all of them need to be miraculous, for he was sent by the All‑Mighty as a human being to guide and lead human beings in their collective affairs and individual deeds to happiness in both this world and the next, and to disclose the wonders of God's art and the works of His Power, each of which is a miracle although it appears to us as ordinary and familiar. If he were extraordinary in all of his acts, he could not guide human beings and instruct them through his acts, states, and attitudes.

Being supplied with some extraordinary phenomena to prove his Prophethood to obstinate unbelievers, he worked miracles when necessary. But his miracles were never such that people were forced to believe against their will, as that would annul human free will in this arena of test and trial. If this were not so, there would have been no choice, meaning that Abu Jahl would have believed as did Abu Bakr and that no one could have been held responsible, in this life and the next, for their deeds.

It is surprising that while so many people believed in him because they saw him perform a miracle, speak some words, or glimpsed his face, some people today go astray as if these thousands of proofs are not enough, although they reach us through authentic lines of transmission and have caused countless discerning people to accept Islam.