A thought from Kotzk:[1]
The verse (Mishlei 23:23) states: “Buy truth and do not sell it.” There are some people that are willing to sell truth to the whole world, except themselves. To these people, the verse states, “Buy truth” for yourself, and don’t merely toil to sell it to your fellow.
[1] Emet Mkotzk Titzmach, Pg. 202.