Why will a Christian enter Hell if he was born Christian?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The Prophet, sallallaahu ‘alayhi wa sallam , said that every child is born with Fitrah (innate nature), and then his parents make him a Jew, Christian or a Magian. [Al-Bukhari and Muslim]

Fitrah means the innate inclination to Islam which is free from false beliefs and which only accepts true ones. If the self is left to its innate nature, it admits the Lordship of Allaah The Almighty, loves Him and worships Him without associating anything with Him. However, it is corrupted by the temptations of the devils whether from among humans or Jinn, including disbelieving parents.

If a disbeliever’s son dies before puberty, the ruling on this person is explained in Fatwa No. 2740.  If the son reaches puberty but continues to be a Christian and dies in this state, he deserves Hell for his own actions, because he has reached the age of responsibility where he is held accountable for his deeds and choices. Allaah The Almighty Says (what means): {Every soul, for what it has earned, will be retained.} [Quran 74:38]

Allaah The Almighty is just and never oppresses anyone. He gave each person a mind, hearing and sight, and established convincing arguments and proofs through which a person can distinguish right and wrong. Allaah The Almighty Says (what means): {And have shown him the two ways.} [Quran 90:10] Thus a person will be rewarded in accordance with the choice he makes and the deeds he does.

Allaah Knows best.