Hebrews 12:12-15  Therefore lift your drooping hands and strengthen your weak knees,  and make straight paths for your feet, so that what is lame may not be put out of joint but rather be healed.  Strive for peace with everyone, and for the holiness without which no one will see the Lord.  See to it that no one fails to obtain the grace of God; that no “root of bitterness” springs up and causes trouble, and by it many become defiled;  that no one is sexually immoral or unholy like Esau, who sold his birthright for a single meal
“Strive for peace and for holiness without which no one will see the Lord”. We are called to be helping each other in our progress to our goal, Jesus Christ. There are two main obstacles to that attack us and seek to make the church no help to anyone in their journey to the Celestial City; a bad relationship with others, and a bad relationship with God.
In-fighting. We can never lift up the drooping hands and strengthen the weak knees of our fellow racers if we are not at peace with them. End of story. Oh the good we could do for one another if there were no conflict.
Lack of personal holiness – there will always be those in the church who need to be helped, but if no one is pursuing a holy life founded upon the grace of God in Christ, there is a serious problem. It is no church of Christ where there is no real, hard fought pursuit of holiness. So the church then in this picture is a fellowship of people all chasing after holiness for themselves and helping others pursue it as well. It is a beautiful picture.
What are the two greatest commandments? That is what this text is about. Loving God supremely and our neighbours as ourselves.
Verse 15 is not the beginning of a new sentence. The flow of thought in verses 14-15 is thus: Strive for peace with everyone and for the holiness without which no one shall see the Lord, seeing to it that no one fails to obtain the grace of God. We strive for holiness making sure that we have truly obtained the grace of God. To strive for holiness or seek to help others strive for holiness must have the grace of the Gospel as its fuel. There will never be holiness if there has been no receiving of grace and growing in grace.
The church is a fellowship of people who preach the Gospel of the free grace of God in Christ, teach the Gospel of the free grace of God in Christ, live out, for the benefit of one another, the free grace of God in Christ. Here is the issue – are we clinging to the Gospel of Jesus Christ? Do we know it? Do we live by it? Do we love it? Do we discuss it with those we worship with, serve with, fellowship with? It is our calling. It is what will help us keep from falling.