‘I marvel that you are so quickly moving from him who called you in the grace of Christ to a different Gospel, which is not another. Only there are some who trouble you and would pervert the Gospel of Christ.'
He cannot understand why they are allowing themselves to be drawn away from God's amazing love and purposes. They have been ‘called in the grace (gracious compassion towards them) of Christ.' In other words, recognising the unmerited favour (grace) being shown to them through what He has done for them on the cross, and hearing in it the call of God, they have responded to Him, receiving forgiveness of sins and being declared righteous before God, thus being ‘engraced' in Christ (Ephesians 1:6). For this is what the Gospel, the Good News of Christ is all about. But now almost unbelievingly they are turning to something else, something which is not really Good News at all. They are listening to men who are distorting the Gospel and robbing it of its glory, men who insist on following sterile religious observances rather than on loving response to Christ, and whose message will turn their glorious good news into a burden.
It was not necessarily the religious observances themselves that were the burden, although in the uncooperative society that they lived in they could be difficult enough, it was the fact that by making necessary for salvation their proper observance of every detail of the Law, they put men onto a treadmill of despair from which they could find no deliverance, as they fought and struggled and failed, and the consequence was that men became terrified because they recognised that they were coming short in them, and life became an endless and continual battle of struggling to dot the right i and cross the right t, a struggle which could in the end only result in failure.
‘Some who trouble you.' The word for trouble is strong and means ‘disturbed' and having ‘conflict of mind' (compare Matthew 2:3; Matthew 14:26; John 14:1). They had previously been at peace as a result of the truth, but now these men have totally disturbed their way of life.