Charles Ellicott Commentary Psalms 69:27

"Add iniquity unto their iniquity; And let them not come into thy righteousness." — Psalms 69:27 (ASV)

Add iniquity: This may be understood in two different senses:

1. Let sin be added to sin in your account, until the tally is full.
2. Add guilt for guilt, that is, for each wrong committed write down a punishment.

And let them not ...: that is, let them not be justified in your sight, nor gain their cause at your tribunal.