Why was Hadrat Ibrahim (as) willing to slaughter his son if killing is an immoral act?

Actions are not good or evil in and of themselves, actions are good or evil because Allah Almighty has taught that they are good or evil. Obedience to Allah Almighty is more important than obedience to any doctrine. Even obedience to a doctrine as important as the unity of God or following His religion is not as important as the principle of obedience to Allah. This point is emphasized in the Holy Quran (Essence of Islam, vol. 4, p. 134):

Say (O Muhammad), ‘If there had been a son to the Gracious God, I would have been the first to worship him.’

(Surah al-Zukhruf, 43:82)

Also, Hadrat Shoaib ^as said:

And it behoves us not to return thereto (to the religion of the disbelievers) except that Allah, our Lord, should so will.

(Surah al-A‘raf, 7:90)

Obviously, it is not possible for God to have a son, or for a Prophet to turn to disbelief, but these points have still been made to emphasize that obedience to a doctrine only has value when it is in obedience to Allah Almighty (Khilafat-e-Rashidah, p. 237).

This same principle applies to the doctrine on the permissibility of taking someone’s life. For example, until the verse of the Holy Quran was revealed prescribing flogging as the punishment for adultery, the Holy Prophet ^sas would instruct that adulterers be stoned to death according to the commandment of the Old Testament (Question Answer Session, August 19, 1984).

The doctrine on permissibility of taking life depends on the commandment of Allah Almighty. Until a commandment is revealed to a prophet, he acts according to the teachings of the previous religion.

To the knowledge of Hadrat Ibrahim ^as, until his time there was no commandment that clearly abolished human sacrifice (Holy Quran English with Short Commentary, p. 912), so he completely submitted to the command of Allah Almighty as he understood it, as did his son. This story carries beauty and significance because, even though he was genuinely mistaken in the interpretation of his visions, but his intentions were ever-inclined to the obedience of Allah Almighty. His actions received such love and affection of Allah Almighty because, “verily deeds are judged by motives.”