Al-Matalib al-'Aliyah 2108 — How the pledge of allegiance is given

It is narrated from Sayyiduna Abu al-Afif (may Allah be pleased with him): I was present when, after the sorrowful passing of the Messenger of Allah (peace and blessings be upon him), Sayyiduna Abu Bakr al-Siddiq (may Allah be pleased with him) was taking the pledge of allegiance from the people. Groups of people would gather around him, and he would say to them: "Pledge allegiance to me on carrying out the commands of Allah Almighty and His Book, and then on hearing and obeying the commander." Abu al-Afif (may Allah be pleased with him) says: I was holding my whip, and in those days I was a youth who had reached puberty or was close to it. So when the people had left and he was alone, I came to him and said: "I pledge allegiance to you on obedience to Allah Almighty and His Book, and on hearing and obeying the commander." The narrator says: (On hearing this) he looked me up and down (carefully).
Imam al-Harith bin Muhammad bin Abi Usamah narrated it in his Musnad al-Harith.