Islam is a condition for the acceptance of deeds

It is narrated from the Mother of the Believers, Sayyidah Umm Salamah (may Allah be pleased with her), that she said: "O Messenger of Allah (peace and blessings be upon him)! Hisham bin al-Mughirah used to feed (people), honour guests, maintain ties of kinship (that is, treat his relatives well) and free captives (she meant prisoners of war), and had he lived to see your time, he would surely have accepted Islam. So will he receive any reward for these good deeds?" Sayyidah Umm Salamah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) said: "The purpose of your uncle's deeds was to gain the world, its fame and its adornment, and not on a single day did he ever make this supplication: 'Rabbighfir li khati'ati yawmad-din' (My Lord, forgive me my faults on the Day of Recompense)."
Imam Abu Ya'la also narrated something similar from Sayyidah Umm Salamah (may Allah be pleased with her) through Abu Khaythamah, Jarir, Mansur and Mujahid.

It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that, while we were staying in Madinah, he said: "On the Day of Resurrection, Islam will come (in bodily form), and Allah, the Mighty and Majestic, will say: 'You are Islam and I am al-Salam (the Source of Peace); today, through you I will give (reward to My servants) and through you I will take (them to account).'"
Imam Abu Dawud recorded this hadith in Kitab al-Zuhd; since al-Hasan al-Basri's hearing from Sayyiduna Abu Hurayrah (may Allah be pleased with him) is not established, this narration is munqati' (broken in its chain) and da'if (weak).

It is narrated from Sayyiduna al-Harith bin Malik al-Ansari (may Allah be pleased with him) that he passed by the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) asked him: "O Harith! In what state have you entered the morning?" He said: "I have entered the morning as a true believer." The Prophet (peace and blessings be upon him) said: "Consider what you are saying, for everything has a reality; so what is the reality of this faith of yours?" He said: "I have turned my soul away from the world; I keep my days thirsty (through fasting) and my nights wakeful (in the worship of Allah). It is as though I am looking at the Throne of my Lord, plainly manifest before me; and as though I am looking at the people of Paradise visiting one another; and as though I am looking at the people of Hell crying out there (from the severity of their torment)." He (peace and blessings be upon him) said three times: "O Harith! You have recognised (the reality), so now remain steadfast upon it."
This narration is from the Musnad of Musaddad, which Imam Ibn Hajar recorded in al-Matalib al-'Aliyah (2873); there is criticism of its chain because of the presence of Ibn Lahi'ah, but its meaning is strengthened by other routes and supporting evidence.