Charles Ellicott Commentary Proverbs 27:1

"Boast not thyself of tomorrow; For thou knowest not what a day may bring forth." — Proverbs 27:1 (ASV)

Boast not thyself of to-morrow. —This is also forbidden in James 4:13 and following, but there on the higher ground that it argues a lack of submission to the will of Almighty God.

This frame of mind, as well as the opposite one of excessive anxiety for tomorrow (Matthew 6:34), proceeds from the same cause: too much dependence upon self. It can only be addressed by learning to realize the love of God for His children (Matthew 6:26, 30, 33) and by looking up to Him daily for protection, guidance, and support.