Why is the promise fulfilled in believers if they are not better at keeping the law than Israel was?

Les explains that the fulfillment is not based on believers being better at law keeping than Israel. It is because of their position and because of the power of the Holy Spirit: they no longer walk after the flesh or after old Adam, but after the Spirit. Just as soon as old Adam is crucified, in God's eyes he is completely dead and out of the picture, though in experience he is still here and defeated. He does not have to remain uppermost; if he does, it is because believers are not fighting the battle. The Holy Spirit came in and empowered the spirit that was in creation—body, soul, and spirit—so that the Spirit working in consort with our spirit enables us to live victoriously. Old Adam is powerful and will come to the fore at times, and that is where the warfare exists. There would be no warfare or battle line without the indwelling Holy Spirit; otherwise we would not stand a chance against the forces of old Adam and Satan. Les also notes that in the Greek it is the Pneuma Hagion, meaning that power from on high.