Matthew Henry Commentary Proverbs 21:30-31

"There is no wisdom nor understanding Nor counsel against Jehovah. The horse is prepared against the day of battle; But victory is of Jehovah." — Proverbs 21:30-31 (ASV)

Means must be used, but, after all, our safety and salvation are only of the Lord. In our spiritual warfare we must arm ourselves with the whole armour of God; but our strength must be in the Lord, and in the power of his might.