When Mark speaks of "sinful people," he is talking about people who commit sins that everyone thinks are especially bad, like stealing or sexual sins. (See: [[rc://en/tw/dict/bible/kt/sin]])
People would fast, or not eat food for a long time, when they were sad or were showing God that they were sorry for their sins. When they were happy, like during weddings, they would have feasts, or meals where they would eat much food. (See: [[rc://en/tw/dict/bible/other/fast]])
The Jewish leaders used rhetorical questions to show that they were angry because of what Jesus said and did and that they did not believe that he was God's Son ([Mark 2:7](./05.md)). Jesus used them to show the Jewish leaders that they were arrogant ([Mark 2:25-26](./25.md)). (See: [[rc://en/ta/man/translate/figs-rquestion]])