New Defender's Study Bible Notes
14:21 any thing whereby thy brother stumbleth. Although any given practice is permissible for a Christian (if not precluded by Scripture, in which case he should abstain from it, even though he would not forfeit his salvation by doing it), he should be willing to give it up if it might injure the faith or testimony of a fellow Christian. There are a number of other Biblical guidelines to help us in making informed decisions about doubtful things. See note under Romans 14:23.