Allaah (al-Ilaah, Eloh-im), the Sublime and Exalted, said in his final revelation to mankind, establishing the truth about Jesus, the Messenger (peace be upon him):

O people of the Scripture (Jews and Christians)! Do not exceed the limits in your religion, nor say of Allaah aught but the truth. The Messiah Eesaa (Jesus), son of Maryam (Mary), was (no more than) a Messenger of Allaah and His Word (through which He created him), (a Word) which He bestowed on Maryam (Mary) and a spirit (Rooh) created by Him. So believe in Allaah and His Messengers. Say not: "Three (trinity)!" Cease! (it is) better for you. For Allaah is (the only) God (worthy of worship), Glory be to Him (Far Exalted is He) above having a son. To Him belongs all that is in the heavens and all that is in the earth. And Allah is All-Sufficient as a Disposer of affairs. (An-Nisa 4:171)

Comments

This verse was revealed in relation to various factions of the Christians (Ya'qubiyyah, Nestoriyyah, Malikaaniyyah, Marqoosiyyah), and they had various sayings so some said, "Jesus is Allaah", others said, "He is the son of Allaah" and others said, "He is the third of three."

Allaah, the Exalted is saying:

O people of the Gospel, do not exceed the true belief in your religion, and do not exaggerate and say of Allaah except the truth. Do not claim a son and wife for Him, for Eesaa (Jesus) the son of Maryam (Mary) was no more than a Messenger like many other Messengers, he was sent with the ultimate truth, which is submitting to Allaah alone without any partners, a truth that is witnessed to by all the signs in creation, and which the innate disposition and natural instinct of every person recognizes, provided it has not been corrupted (through nurturing upon false religion). So Jesus is the Messenger of Allaah. And likewise He is the Word of Allaah, with the meaning that he was created through a Word spoken by Allaah which is "Be!" (not that he, Jesus, in his essence, is the actual Word of Allaah) and with this Word, Jibreel was sent, and Jibreel breathed into Maryam (peace be upon her) from the Spirit of Allaah, the Spirit is a created entity, not something that is from Allaah's essence, but the word Rooh (Spirit) is used to refer to a created entity, and the Rooh (Spirit) was also breathed into Aadam (peace be upon Him) - and none knows the reality of this Rooh save Allaah - so this Rooh (Spirit) was breathed into Maryam (peace be upon her) by Jibreel, so Jesus is the Spirit of Allaah, in this sense, in that he was created through Allaah's sending of the Rooh (Spirit) with Jibreel and the breathing of this spirit into Maryam (peace be upon her). This is the truth, so believe in it, and believe in this truth regarding Jesus, Son of Mary, and submit to Allaah alone, and worship Him alone, and shun the worship of all other deities including Jesus and his mother Mary, for they were mere mortals, who ate and drank, and Allaah chooses whomever He wills for Prophethood. And do not say "There are three (deities)", for there is only one deity in truth. For you have unjustly raised him (Jesus) from the station of Prophethood and Messengership to one of Lordship (Rububiyyah), yet Jesus and his mother Mary are mere mortals, they eat and drink and walk the earth, and they own and control nothing of the heavens and earth, save that Allaah gave miracles to Jesus as a sign of his prophethood and as a evidence to Banee Israa'eel (Children of Israel) that he is indeed sent by Allaah. So if you desist from saying this statement of "Three" it is better for you, because this is the way of deliverance, to believe in the unicity of Allaah, His sole right to be worshipped, He is sanctified and too sublime that He should have a son, rather to Him belongs the heavens and the earth, so everything is under His dominion, and everything is subservient to Him and sufficient is He alone as a disposer of all affairs.

Just as this verse was revealed to correct the exaggeration (ghuluww) of the Christians, it was also revealed to correct the belittlement and rejection of the Jews of the Messiah Jesus and so in this verse Allaah establishes that Jesus is the Messenger of Allaah, the Word of Allaah and the Spirit of Allaah (as explained above). And with this Allaah, the Exalted has established the truth for the People of the Book, both Jews and Christians.

References:

• Tafsir al-Tabari, Tafsir Ibn Kathir, Tafsir al-Baghawi
• Tafsir al-Sa'dee, Tafsir al-Muyassar