Listen to this good news from Allah. Those who embrace this religion from the People of the Book - from the Jews and Christians - will be given a double reward, due to their belief in their Messenger and their belief in Muhammad PBUH.
Allah says: "Those to whom We gave the Scripture before it - they believe in [the Quran]. And when it is recited to them, they say: 'We
believe in it. Verily, it is the truth from our Lord. Indeed we were, [even] before it, Muslims [submitting to Allah].' These will be given their reward twice over, because they are patient, and repel evil with good, and spend (in charity) out of what We have provided them." [28:52- 54]