Is a Christian, who knows that ‘Eesaa (Jesus) and Muhammad, may Allaah exalt their mention, are Prophets, obliged to follow the Islamic religion; as whoever chooses a religion other than Islam, it will not be accepted from him?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His Slave and Messenger as well as that of his family and all his companions.

Whoever amongst the people of The Book stays on his   religion after Muhammad was sent as a Prophet, is not on a correct religion, rather he is on a false religion. Just knowing that Muhammad is a Prophet is not considered as embracing Islam, if this is not accompanied by his obedience and abiding by what he was sent with. The people of The Book whom the Quran declared as non-Muslims and disbelieves and whom the Prophet fought against, did know that he was sent by Allaah in the same manner each one of them knew his child. Knowing this fact did not make their blood sacred and did not turn them into Muslims. Allaah Says (what means): {Those to whom We gave the Scripture know him [i.e. Prophet Muhammad ] as they know their own sons. But indeed, a party of them conceals the truth while they know [it].}[Quran 2:146]. No one can become a Muslim unless he declares the two testimonies of faith and fulfils their conditions, among which is to abide by what Allaah Says and what the Prophet said. Ibn Taymiyyah said: 'The reality of religion is obedience and submissiveness, and this can only be achieved by action and not by words only. Whoever does not perform acts of worship to Allaah, in reality he did not follow the religion, and whoever does not follow the religion, he is a non-Muslim.'

Allaah Knows best