Charles Ellicott Commentary Galatians 5:25

"If we live by the Spirit, by the Spirit let us also walk." — Galatians 5:25 (ASV)

If we live in the Spirit.—It seems, on the whole, best to translate: If we live by the Spirit; if we derive our life from the Spirit; if it is by the action of the Spirit that our moral activity as Christians is kept alive. At the same time, another way of taking the words is possible: If we live to the spirit, following the analogy of Romans 14:8: Whether we live, we live unto the Lord, and so on.

Let us also walk in the Spirit—that is, by the rule of the Spirit, as the Spirit dictates (compare Galatians 5:16, and the Note). The life which the Spirit gives life to needs human cooperation, an active effort on the part of the Christian, to realize it completely in practice. St. Paul first sets before his readers what God has done for them, and then uses this as an argument and stimulus to renewed efforts on their own part.