Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) says regarding this verse: "Our Lord! We have believed, so record us among the witnesses" [Surah al-Ma'idah: 83]. He said: "That is, with Muhammad (peace and blessings be upon him) and his Ummah, for they bore witness that he (peace and blessings be upon him) conveyed the message, and they also bear witness for the messengers that they conveyed their message."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11682