Possible meanings are 1) "I have seen that all perfect things eventually cease," referring to the best things that people can do, or 2) "I have seen that everything has limits."
God's command always being true and perfect is spoken of as if God's command were an object that is very wide. Alternate translation: "but your command is without limits" or "but your command is eternal" (See: [[rc://en/ta/man/jit/figs-metaphor]])