13 You, my brothers and sisters, were called to be free. But do not use your freedom to indulge the flesh; rather, serve one another humbly in love. 14 For the entire law is fulfilled in keeping this one command: “Love your neighbor as yourself.” 15 If you bite and devour each other, watch out or you will be destroyed by each other.
A new development in the argument is now seen in 13. The words 'called into liberty' sum up all that has thus far been said in the chapter, but now the Apostle turns to warn his readers of the danger of allowing liberty to become licence. To be free from the law does not mean to be free to sin. Paul's doctrine of freedom does not remove the restraints that keep men from licence and immorality, and to interpret it as if it did is simply to misunderstand it completely. The alternatives here as 'an occasion to the flesh' and 'by love serve one another', and what Paul is insisting is that, in the new order of existence into which we are brought by the Spirit of God in the gospel, 'love' and not 'the flesh' is the controlling factor ('the flesh' refers to fallen human nature, that element in man's nature which is opposed to goodness, and makes for evil). To give occasion to the flesh is simply to be in bondage, and means that we have not understood what it means to have been set free in Christ. This corresponds to the teaching in Romans 6:1ff, where Paul avers that to say 'Shall we continue in sin that grace may abound?' is completely to misunderstand what it means to have 'grace reigning through righteousness' (Romans 5:21). For just as to be 'under sin' and 'under the law' means to be in the control of sin and law, so to be 'under grace' means to be in the control of grace and under its blessed dominion. The flesh is not allowed to 'have occasion' when grace dominates the life. That is Paul's point.