The Messenger (Muhammad SAW) believes in what has been sent down to him from his Lord, and (so do) the believers. Each one believes in Allah, His Angels, His Books, and His Messengers. They say, "We make no distinction between one another of His Messengers" - and they say, "We hear, and we obey. (We seek) Your Forgiveness, our Lord, and to You is the return (of all).
Surah (Chapter) al-Baqarah (The Cow) The Qur-an 2:285

And (remember) when Allah took the Covenant of the Prophets, saying: "Take whatever I gave you from the Book and Hikmah (understanding of the Laws of Allah, etc.), and afterwards there will come to you a Messenger (Muhammad S) confirming what is with you; you must, then, believe in him and help him." Allah said: "Do you agree (to it) and will you take up My Covenant (which I conclude with you)?" They said: "We agree." He said: "Then bear witness; and I am with you among the witnesses (for this).
Surah (Chapter) Al-‘Imran (Family of ‘Imran) The Qur-an 3:81