Zubair bin ‘Abdul Muttalib mentioned this pact in his poetry saying:
إن الفضول تحالفوا وتعاقدوا ألا يقيم ببطن مكة ظالم
Indeed the three Fadhls (Fadhl bin Fudhaalah, Fadhl bin Wadaa‘ah and Fudhail bin Haarith) all took a solemn pledge from the people that no oppressor would be permitted to live within the valley of Makkah
أمر عليه تعاهدوا وتواثقوا فالجار والمعتر فيهم سالم
They all pledged and agreed to this, and hence the neighbors and visitors would all be safe among them in Makkah.”
(Extracted from Seeratul Mustafa 1/94)