The Pact of the Virtuous (Hilf al-Fudul)

Clans of Quraish pledge to stand with anyone wronged in Makkah, after a merchant of the Zubaid clan is cheated of his payment. Years later the Prophet ﷺ says he would still answer such a call in Islam.

As the book dates it: at the end of the Fijar wars

It was more appealing to me than herds of cattle.