The Family Of Imran - 3:86
How can Allah guide a people who disbelieve after they have believed and witnessed that the messenger is true and clear proofs have come to them? Allah does not guide the unjust people.
The testimony of the Jews and Christians that the Messenger (Muhammad) was true:
The Heights/7:157
Indeed, they follow (when the time comes) that messenger whom they find written in the Torah and the Gospel with them, the Messenger of Allah, the Messenger of the Ummim (who has not read the Torah and the Gospel), who enjoins upon them good and forbids them from evil, who makes lawful for them good things and forbids for them unclean things, who removes from them the weights and the fetters that weigh them down. Those who believe in him and respect him and help him and follow the light sent down with him are the successful ones.
The Night Journey/17:107
"Say: "Believe in it or not!"When it is recited to those who have been given knowledge before, they fall on their faces in prostration"
The Night Journey/17:108
"Great is our Lord. The Word of our Lord has come true,"they say"
The Ranks/61:6
"Remember when Jesus said to his people: "O Children of Israel, I am a messenger of Allah sent to you, confirming the Torah before me and giving good tidings of a messenger to come after me whose name is more praised."Then when he showed them clear proofs, they said, "This is a clear magic."