Which of these sins are minor and which are major: masturbation, kissing one's sister, looking at pornographic images, and shaking hands with a non-mahram woman?

Kissing one's sister is permissible if it is not out of lust and not on the mouth. Scholars have permitted it for someone returning from a journey. If these conditions are not met, then it is forbidden and is considered a minor sin. A major sin is defined as a sin for which there is a prescribed punishment (hadd) in this world, or a warning of punishment in the afterlife, or a curse upon its perpetrator. Persistence in a sin transforms it into a major sin. It has been said: "No sin is minor when persisted in, and no sin is major when repentance is sought."

The Hadith states: "Beware of minor sins, for they accumulate upon a person until they destroy him."