Allah sent any prophet—it therefore includes the Islam embraced by every nation that truly followed its messenger.

The messengers were sent to proclaim the oneness of worship

The very core of Islam, in every sense, is the testimony la ilaha illa Allah (there is no deity worthy of worship except Allah). Through this declaration Allah sent all His messengers. He, the Exalted, says: “We certainly sent into every nation a messenger, [proclaiming], ‘Worship Allah and shun all false gods’” (16:36). He also says: “We never sent a messenger before you without revealing to him: ‘There is no deity but Me, so worship Me’” (21:25).

Concerning Abraham, the Intimate Friend, He says: “When Abraham said to his father and his people, ‘I disown whatever you worship • except the One who created me, for He will surely guide me,’ he made that word endure among his descendants so that they might return” (43:26-28). He likewise says about him: “Have you considered what you and your forefathers have been worshipping • they are all enemies to me, except the Lord of all worlds” (37:85-87). And He, Most High, says: “You have an excellent example in Abraham and those who were with him when they said to their people, ‘We disown you and whatever you worship besides Allah; we reject you, and between us and you enmity and hatred have appeared forever—until you believe in Allah alone’” (60:4).

He further says: “And ask those of Our messengers whom We sent before you…”