Yazid bin Amirah (may Allah have mercy on him) said: When death approached Sayyiduna Mu'adh (may Allah be pleased with him), he said: Seek knowledge with four people: with Uwaymir Abu al-Darda', with Salman al-Farisi, with Abdullah bin Mas'ud, and with Abdullah bin Salam, for I heard the Messenger of Allah (peace and blessings be upon him) say: "He is the tenth of ten."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17365