Ye did run well; who did hinder you that ye should not obey the truth? Ye did run well - Ye once had the faith that worked by love - ye were genuine, active, useful Christians.
Who doth hinder - Who prevented you from continuing to obey the truth? Ye could only be turned aside by your own consent. St. Paul here, as in 1 Corinthians 9:24 (note), compares Christianity to a race. See the notes on the above text.