18For if the inheritance [of what was promised] is based on [observing] the Law [as these false teachers claim], it is no longer based on a promise; however, God granted it to Abraham [as a gift] by virtue of His promise.
18The great gift that God has for us does not depend on the law. If it did, it would no longer depend on the promise. But God gave it to Abraham as a free gift through a promise.
18God has promised to give good things to his children. But that does not happen as a result of God's Law. If that were true, then we would not receive God's good things as a result of his promise. But God gave those good things to Abraham as a gift, because he had promised to bless Abraham.