'Back part' in the Bible

And kept back part of the price, his wife also being privy to it, and, bringing a certain part, laid it at the feet of the apostles.

And to keep back part of the price of the land? While it remained, did it not remain thine? And when it was sold, was it not in thy power? Why hast thou conceived this thing in thy heart? Thou hast not lied to men, but to God.