Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) said: (Regarding the explanation of this verse «مَنجَاءَبِالْحَسَنَةِفَلَهُخَيْرٌمِّنْهَاوَهُممِّنفَزَعٍيَوْمَئِذٍآمِنُونَ» “Whoever does good, there is something better for him, and they will be safe from the terror of that Day.”) He said: “By this, «لا اله الا الله» is meant.” And «وَمَنجَاءَبِالسَّيِّئَةِفَكُبَّتْوُجُوهُهُمْفِيالنَّارِ» “Whoever does evil, they will be thrown down on their faces into Hell. (That evil) is shirk (associating partners with Allah).”
Hadith Referenceمسند اسحاق بن راهويه / كتاب الايمان / 35