Sayyiduna Jarir (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Islam is built upon five things: testifying that there is no true god except Allah, establishing the prayer, giving zakah, performing Hajj to the House (of Allah), and fasting in Ramadan."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2351
Sayyiduna Jarir (may Allah be pleased with him) came to the Prophet (peace and blessings be upon him) to give him the pledge of allegiance, and he (peace and blessings be upon him) said: "O Jarir, stretch out your hand." He asked: On what? He (peace and blessings be upon him) said: "On condition that you surrender yourself to Allah, and that you wish well for every Muslim." Sayyiduna Jarir (may Allah be pleased with him) understood this, and he was an intelligent man, so he said: O Messenger of Allah, as far as I am able. So this became a concession for people after him.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2352
It is narrated from Sayyiduna Jarir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "When a slave runs away and joins the enemy, and dies in that state, he dies a disbeliever."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2353