In the Qur'an, Jesus has been given a number of honourable titles. Apart from being known as the son of Mary and the Messiah, he is the aya(sign). The sign not only to the Israelites but to the world (Surah 19:21; 21:91; 23:50-52; 3:44-50). Jesus is also mentioned as a mathal(example or likeness) in the Qur'an. He is an example for the people (Surah 43:57, 59). In another place he is likened to Adam (Surah 3:52-59).
The Qur'an depicts Jesus also as rahma (mercy) from God for all people (Surah 19:21). However, for Muslims it is the Qur'an that is the expression of the rahma of God (Abdoldjavad Falaturi, Muslim thoughts for Teachers and textbooks authors, p.18. Croydon: Islamic Scientific Academy, 1990). Since God is eternal, the Qur'an as his rahma and word is eternal and uncreated. This interpretation is similar to the Christian doctrine of the pre-existence of Jesus as the Word (Greek: logos), presented in John 1:1.
Jesus is described as one who is min al-muqarrabin (among the nearest to God) and as min al-salihin (of the upright) and as wajih (eminent) [Surah 3:40-46]. Baidhawi amplifies this, saying that Jesus is illustrious in this world as a Prophet and in the next as an intercessor (Hughes, Dictionary of Islam, p.229.) Following the Qur'anic presentation of Jesus, he is known among Muslims as Kalimatullah (the word of God), and Ruh Allah (the spirit of God) [Surah 3:45; Surah 4:171]. No other prophets have been described in such terms. No other prophet nor Muhammad has ever been called the spirit of God.
Islamic belief is incomplete without a belief in Jesus. In some traditions the belief that Jesus is the word and spirit of God, is considered as an essential item of faith along with the belief in the Muslim Shahadah (Creed): Narrated Ubada: The Prophet said, 'If anyone testifies that none has the right to be worshipped but Allah alone who has no partners, and that Muhammad is His Slave and His Apostle, and that Jesus is Allah's Slave and His Apostle and His Word which He bestowed on Mary and a Soul from Him, and that Paradise is true, and Hell is true, Allah will admit him into Paradise with the deeds which he has done even if those deeds were few' (Sahih Bukhari, Vol. 4, Hadith 644). In other words, belief in Jesus can earn a soul the paradise of God. Yet Muhammad in other traditions is quoted as saying that he could not give that assurance himself.