Sayyiduna Ibn Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "The safeguard of the people of the earth from drowning is the bow (the rainbow), and the safeguard of the people of the earth from mutual discord is allegiance to Quraysh, the household of Allah; whichever tribe of the Arabs opposes it will become the party of Iblis."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11431