Proverbs 23:23:
Buy truth, and do not sell it; buy wisdom, instruction, and understanding.
“Buy truth” = you can know truth. It’s obtainable.
“Buy truth” = it’s worth getting. That is, it is valuable.
“Do not sell it” = states the same thing from another angle: it’s valuable. Hold on to it. It’s worth keeping.
(From Jon Rittenhouse, A Biblical View of Truth.)