Al-Matalib al-'Aliyah 772 — The states of the dying person

It is narrated from Imam Makhul (may Allah have mercy on him) that Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) fell ill, and his companions came to visit him. He said: "Sit me up." So his companions sat him up. Then he (may Allah be pleased with him) said: "I heard a blessed saying from the Messenger of Allah (peace and blessings be upon him); he (peace and blessings be upon him) said: 'Whoever's last words at the time of death are "La ilaha illallah, wahdahu la sharika lah" (there is no true god except Allah, He is alone, He has no partner), this word wipes out all his previous sins and errors; so prompt your dying ones to say it.'" The people said: "O Abu Abd al-Rahman (Sayyiduna Mu'adh)! How is this word for the living (in reward)?" He said: "It wipes out and removes (their sins) even more."
Imam Abu Ya'la narrated this hadith in his Musnad. Its chain contains a narrator named Faraj bin Fadalah, who is da'if (weak) according to the majority of hadith scholars; however, the virtue of prompting the testimony of faith and of its being the last words is also established by other sahih hadith.