Commentaries:
Robertson's Word Pictures (NT)
Swear not at all (mh omosai olwv). More exactly "not to swear at all" (indirect command, and aorist infinitive). Certainly Jesus does not prohibit oaths in a court of justice for he himself answered Caiaphas on oath. Paul made solemn appeals to God (I Thessalonians 5:27; I Corinthians 15:31). Jesus prohibits all forms of profanity. The Jews were past-masters in the art of splitting hairs about allowable and forbidden oaths or forms of profanity just as modern Christians employ a great variety of vernacular "cuss-words" and excuse themselves because they do not use the more flagrant forms.
Other Robertson's Word Pictures (NT) entries containing Matthew 5:34:
Matthew 5:42
Matthew 23:16
1 Corinthians 5:1
James 5:12
2 Peter 3:16
Revelation 4:2
Revelation 10:6
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