Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage. Stand fast therefore in the liberty - This is intimately connected with the preceding chapter: the apostle having said, just before, So then, brethren, we are not children of the bond woman, but of the free, immediately adds, Stand fast therefore in the liberty wherewith Christ hath made us free. Hold fast your Christian profession; it brings spiritual liberty: on the contrary, Judaism brings spiritual bondage. Among the Jews, the Messiah's reign was to be a reign of liberty, and hence the Targum, on Lamentations 2:22, says: "Liberty shall be publicly proclaimed to thy people of the house of Israel, על יד משיחא al yad Mashicha, by the hand of the Messiah, such as was granted to them by Moses and Aaron at the time of the passover."
The liberty mentioned by the apostle is freedom from Jewish rites and ceremonies, called properly here the yoke of bondage; and also liberty from the power and guilt of sin, which nothing but the grace of Christ can take away.