KJV:
And thou shalt keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the LORD thy God, according as the LORD thy God hath blessed thee:
NASB:
"Then you shall celebrate the Feast of Weeks to the LORD your God with a tribute of a freewill offering of your hand, which you shall give just as the LORD your God blesses you;