That verse clearly states that The Messengerﷺbelieves in what has been revealed to him from his Lord, and so do the believers. All of them believe in Allah, His angels, His books, and His messengers. They do not differentiate between any of His messengers. They say: “We hear and we obey. We seek Your forgiveness, our Lord, and to You is the return.”
The meaning is straightforward. The Prophet Muhammad ﷺ believes in the revelation given to him. Not only him, but the believers also believe in Allah, His angels, His revealed books, and all His messengers. Believing in Allahﷻ alone is not enough; one must also believe in angels, scriptures, and all prophets. A person cannot say he believes in one prophet and reject another. All are messengers of Allah.
The believers declare that they hear and obey, and they ask Allahﷻ for forgiveness. Allahﷻ records this so that later generations will follow the same belief and attitude: complete faith and obedience.