David asked the Lord to deal with him in harmony with His loyal love: for the sake of God"s reputation, David"s need, and the sinfulness of the wicked. David had sought to follow the Lord faithfully, and God had promised to bless people who did that. However, David was not experiencing God"s blessing. This made other people question God"s justice and faithfulness. If God would again bless David and curse his enemy, this would show onlookers that God"s promises are trustworthy. In these verses, David described how he felt in his downtrodden condition. [source][source][source]
The Israelites usually practiced fasting ( Psalm 109:24) for spiritual reasons, rather than for physical reasons like losing weight. They went without food and sometimes drink, temporarily, to spend that time in a more important activity, specifically: seeking God in prayer. Therefore we should probably understand David"s reference to fasting as including prayer. He had prayed earnestly about the situation this psalm reflects. His extended prayer and fasting had made him physically weak. [source][source][source]
The people who reproached David ( Psalm 109:25) were evidently his enemies. These are the other people in view throughout the psalm. [source][source][source]