The Holy Quran says:
99:7 And so, he who shall have done an atom’s weight of good, shall behold it;
99:8 and he who shall have done an atom’s weight of evil, shall behold it.
(Muhammad Asad translation)
God takes into account even our smallest actions to the point that not even an atom of good or evil escapes His notice. The receipt you picked up off the floor, the smile you gave to your grandmother, the way you said “thank you” to the girl at the ice cream shop, and so many little deeds that we forget about actually matter. How sad, no, tragic would it be to be denied heaven because of a few little deeds? Of course God is Merciful and no one can even imagine the extent of His Mercy, but He reminds us that the little things do count.
Little bad deeds count as well. In English, we have the terrible phrase “white lie.” We think that some acts of dishonesty are minor or trivial. Perhaps they are trivial to us, but what about to the person to whom we lie? And what about God? What does He think of these lies?
In another place in the Quran, God says, “It is most hateful in the sight of Allah that ye say that which you do not.” (61:3, translation by Muhammad M. Pickthall) The type of lie where one says something but fails to deliver on it is deeply hated by God. An example might be a father telling his daughter he will take her to the zoo if she behaves and then neglecting to take her. We should remember that God chose man above all animals to empower with the gift of speech. To twist that gift into a tool for evil is a great crime.
But we should not despair. Even though we know that we will see the results of even an atom’s worth of evil, we should not give up hope for heaven. If we beg Allah for forgiveness and sincerely repent of our bad deeds, we can overcome our sins.