John Gill Commentary Psalms 109:25

"I am become also a reproach unto them: When they see me, they shake their head." — Psalms 109:25 (ASV)

I became also a reproach to them
Or they reproached him; not only in life, traducing his conversation, blaspheming his miracles, calling him a Samaritan, saying he had a devil, and charging him with sedition; but at the time of his death they reviled him, and treated him in the most opprobrious manner.

When they looked upon me, they shook their heads ;
which was verified in the Jews as they passed by the cross of Christ, where they came to stare upon him and scoff at him, (Matthew 27:39) .