Praise be to God.
Tim, this is a reply to the question about sin. God obviously knows better than me about it, but I will try to give a brief outline of sin as I understand it, and if the Qur’an says anything other than what I say, please take the quranic teaching, not my error.
As I understand it, sin, by itself, doesn’t lead to punishment, for God is merciful. Rather, sin leads to trial, and regret, and then repentance is required. If there is no repentance, then sin must eventually be a cause of retribution. Divine justice requires this. Adam learned repentance from God.
God is the forgiver of sin. Most sins require repentance to get forgiveness, although others are forgiven without repentance. Some sins are minor and will be forgiven by simply being good, without particular repentance.
All sins are capable of being forgiven, with the exception of wilful paganism or polytheism committed after proper knowledge of God is established by that person. That is to say that shirk (association of partners in the Godhead, division of the Godhead, ascribing divinity to created things, etc.) is forgiven if done in ignorance but not if done wilfully.
There are certain sins which require hadd punishment, that is prescribed punishment given by God through revelation. These are theft (if repeat offender), fornication, adultery, murder, manslaughter, etc. These are judged administered by religious courts, and the punishments include capital punishment, fasting a certain number of days, expiation by feeding of a certain number of needy people, and compensation money. God knows best.
As explained in the Qur’an, God has many names. In Arabic, ‘Gaffur’ is the Oft-forgiving, and ‘Raheem’ is the giver of mercy, so when Muslims repent they call on God by these names, and also Tawaab, which means the acceptor of repentance. Muslims do this because the Qur’an says to call on God by his names.
Sebastian
And, we understand that Adam sinned, because he disobeyed a command of God, and that all the children of Adam sin. All people sin, for no-one is perfect - only God is perfect - and all prophets make sins but they are forgiven because that is the destiny of the world and they have been chosen in that way. God knows best about the prophets, but for a Muslim it is not that a prophet is sinless - rather, they are chosen and they will receive God’s mercy. Abraham, Moses, Jesus, and Mohammad all prayed to God for help. They are mortal, are human, they ate food, and they seek nearness to God.