They were willing of themselves. — Literally, spontaneously. This was the point of excellence which he wished to indicate as an example to the Corinthians. Those of Macedonia needed no appeal or counsel such as he had given to the Corinthians and to others.
Related Commentaries of 2 Corinthians 8:3
2 Corinthians 8:3
3 For to their power, I bear record, yea, and beyond their power they were willing of themselves;