It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "I asked my Lord, the Mighty and Majestic, for three things for my Ummah; He granted me two and withheld one from me. I said: 'O my Lord! Do not destroy my Ummah through hunger.' He said: 'This is granted to you.' I said: 'O my Lord! Do not give an enemy from other than themselves - meaning the polytheists - power over them, so that it uproots them.' He said: 'This too is yours.' I said: 'O my Lord! Do not let their fighting be among themselves,' and He withheld this (third) from me."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 178