The Promise of Abdul Muttalib

When the Well of Zamzam was dug again, Quraish tribe shared the well with Abdul Muttalib, because he had no children except al-Harith. Abdul Muttalib asked Allah to give him ten children.

He promised that if Allah would give him ten sons, he would sacrifice one of them for the sake of Allah.

This happened before Islam, and Abdul Muttalib didn't know that sacrificing his son is forbidden (haram). But Abdul Muttalib wanted to do something for the sake of Allah.