That even Barnabas should be carried away was an especial cause of surprise and sadness to Paul. Barnabas had stood by him in all the disputes that he had had with the Judaizers.
When we say that God uses human instruments, we do not mean that God takes over from them so that they pass through all difficulties without feeling the weight of those difficulties. God throws the burden first of all entirely on his human instruments; only then can they cast their burdens upon the Lord. We may have dear friends in Christ and those who bring us encouragement in the Lord’s work, but ultimately we must rest on God alone. For even the best go astray at some point. In such trials, the true foundation of our faith is exposed.