What is sin?
1 John 3
4Everyone who sins breaks God's law, because sin is the same as breaking God's law. 5 You know Christ came to take away our sins. He isn't sinful, 6and people who stay one in their hearts with him won't keep on sinning. If they do keep on sinning, they don't know Christ, and they have never seen him.
7Children, don't be fooled. Anyone who does right is good, just like Christ himself. 8Anyone who keeps on sinning belongs to the devil. He has sinned from the beginning, but the Son of God came to destroy all that he has done. 9God's children cannot keep on being sinful. His life-giving power+ lives in them and makes them his children, so they cannot keep on sinning. 10You can tell God's children from the devil's children, because those who belong to the devil refuse to do right or to love each other.
"The Prophet (Muhammad) said, "Piety is good manner,and sin is that which creates doubt and you do not like people to know it." Sahih Muslim 32;6195
“For in God's sight are (all) his servants, (namely), those who say: 'Our Lord, we have indeed believed: forgive us, then, our sins ("dhunub"), and save us from the agony of the Fire.” Quran 3: 15–16
“If you avoid great sins (kaba’ir or dhanb) which are forbidden you, We will remit from you your evil deeds (sayyi’a).” Quran 4: 31
“And whoever does a wrong or wrongs himself but then seeks forgiveness of Allah will find Allah Forgiving and Merciful. And whoever commits a sin only earns it against himself. And Allah is ever Knowing and Wise.” Qur’an 4: 110-111