Since I came from the Bible to the Quran, I think my task is to show what both books have in common.
A Muslim is purified through the word of Allah.
This process of purification has its counterpart in the Bible. When someone reads about baptism, he might wonder about the function of the pouring of water on the head of the believer. It is clear that the literal meaning does not make any sense, so one must look for the spiritual meaning. So I found out that one of the many symbols for the word of God is the word „water“, which means the believer should be baptized with the word of God.
Muhammad described that Jesus was able to speak with the word of Allah, since the holy Ghost was dwelling in him. So the holy Ghost is closely related to the word of Allah. Furthermore the Bible describes that the holy Ghost is dwelling in the heart of man. So when the word of Allah has its place in the heart of man, he is purified.
This process, the change of the heart of the believer through the word of Allah, is called baptism.