Musnad Ahmad 6:23

Qutaybah ibn Sa'id narrated to us, Bakr ibn Mudar narrated to us, from Ibn al-Had, from Muhammad ibn Ibrahim, from Abu Salamah ibn 'Abd al-Rahman, from Talhah ibn 'Ubayd Allah: That two men came to the Messenger of Allah (peace and blessings of Allah be upon him), and their conversion to Islam was together. One of them was more diligent than his companion. The diligent one among them went out to fight and was martyred. Then the other remained after him for a year, then he passed away. Talhah said: I saw in what a sleeper sees as if I were at the gate of Paradise, and behold, I was with them both. Then someone came out from Paradise and gave permission to the one who died last among them. Then he came out and gave permission to the one who was martyred. Then they returned to me and said to me: "Go back, for your time has not yet come." Talhah woke up and began telling the people about it, and they were amazed by that. That reached the Messenger of Allah (peace and blessings of Allah be upon him), so he said: "What are you amazed at regarding that?" They said: "O Messenger of Allah, this one was more diligent, then he was martyred in the way of Allah, yet this one entered Paradise before him." He said: "Did he not remain after him for a year?" They said: "Yes." He said: "And did he not reach Ramadan and fast it?" They said: "Yes." He said: "And did he not pray such and such prostrations in the year?" They said: "Yes." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Then the distance between them is as the distance between the heaven and the earth."