This verse was recited in the presence of Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), or he recited it himself: "Indeed, Ibrahim was an ummah (one combining all good qualities), devoutly obedient to Allah" [Surah al-Nahl: 120]. Sayyiduna Abdullah (may Allah be pleased with him) said: Indeed, Mu'adh was an ummah, devoutly obedient to Allah. The people said: O Abu Abd al-Rahman! (The verse is:) "Indeed, Ibrahim was an ummah, devoutly obedient to Allah." Sayyiduna Abdullah (may Allah be pleased with him) said: Do you know what an ummah is? It is the one who teaches people goodness. And the qanit is the one who obeys Allah and His Messenger.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9907