For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise.
The inheritance - all the blessings inherited by Abraham's spiritual children, according to the promise to him and to his seed, Christ, justification and glorification (Romans 8:17; 1 Corinthians 6:9; Galatians 4:7).
But God ... - Greek order, 'But to Abraham it was by promise that God hath gratuitously given х kecharistai (G5483)] it.' The conclusion is, Therefore the inheritance is not of, or from, the law.