Jareer, may Allah be pleased with him, said, “I pledged allegiance to the Prophet (peace be upon him) to establish the prayer, give the Zakat and advise every Muslim.” (Al-Bukhari and Muslim)

Ibn Hibban narrated (this Hadith) by way of Abu Zur’ah Bin Amru Bin Jareer on the authority of his grandfather (i.e Jareer) and added: So whenever Jareer used to buy or sell something he used to say, “Know that what I have taken from you is more valuable than what I have given you, so choose.” (Fath Al-Bari, 1/139)

Indeed Jareer honored his pledge to the Prophet (peace be upon him). He once asked his servant to buy a horse for him, so he bought one for 300 dirhams and brought it with its owner to Jareer. Jareer said to the owner, “Your horse is worth more than 300.” He then bought it from him for 800 dirhams. When Jareer was questioned about this, he said, “Indeed I pledged allegiance to the Prophet (peace be upon him) to give advice to every Muslim.” (At-Tabarani, Ad-Dibaj ‘Ala Muslim, 1/75)

Ziyad Bin ‘Ilaqah said: I heard Jareer Bin Abdullah speak on the day that Caliph Al-Mugheerah Bin Shu’bah died. He stood up (on the Minbar), praised Allah and said:

“Have Taqwa of Allah alone and do not associate any partners with Him. Be solemn and calm until another leader is appointed to you, for indeed he will now come.” He then said: “Ask forgiveness for you leader (Al-Mugheerah) for indeed he loved forgiveness.” He continued, “Amma ba’d. Indeed I approached the Prophet (peace be upon him) and told him that I would pledge allegiance to him upon Islam. So he stipulated upon me that I advise every Muslim, so I pledged allegiance to him upon that (with these two hands of mine). By the Lord of this Masjid, indeed I am a sincere adviser to you all.” He then sought forgiveness from his Lord and descended (from the Minbar). (Al-Bukhari)

Imam Al-Bukhari concluded the “Book of Iman” with his advice to people to act upon authentic Ahadith as opposed to inauthentic Ahadith. He then finished the ‘Book of Iman’ with Jareer’s sermon which expresses his own state while authoring his book. (Fath Al-Bari, 1/140)