Al-Matalib al-'Aliyah 2895 — hadiths 2892–2897

Ibn al-Daylami narrates from one of the three men who used to serve Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) that when the time of death of Sayyiduna Mu'adh (may Allah be pleased with him) drew near, I said to him: "Do I not see that your final hour has arrived?" He said: "Yes, and what an evil time this is for lying. (Listen!) Whoever dies in a state of firm certainty about three things: that he knows that Allah Almighty is the Truth, that the Hour will certainly be established, and that Allah Almighty will raise again all those who are in the graves," the narrator said: Then he said something by which he encouraged them (towards good); if those words were not "he will certainly be forgiven", then I do not know (the exact words).
There is an unnamed narrator (a servant of the Companion) in the chain of this hadith; however, on the basis of other supporting evidence its meaning is sound and established.