Is the fast of a Christian who fasts Ramadan but does not pray valid?

The fasting of a Christian who does not pray is of no benefit to him, for disbelief nullifies good deeds, and the condition for the validity of acts of worship is Islam. Therefore, he should be invited to Islam and guided to believe in the Prophet Muhammad, may Allah’s peace and blessings be upon him, and to believe that Allah is One and has no partner, and that the Messiah Jesus, peace be upon him, is a servant of Allah and His Messenger, not His son. If he embraces Islam, then he must perform the prayer, fasting, zakat, and Hajj. He will have the rights of Muslims and be subject to the same obligations.