Let your conduct be without covetousness; be content with such things as you have. For He Himself has said, “I will never leave you nor forsake you.” So we may boldly say: “The LORD is my helper; I will not fear. What can man do to me?”
The natural human tendency is to focus on the physical. Sometimes we desire more money and possessions for enjoyment, but in worrisome times our lack of contentment can be driven simply by a desire for financial security.
Thankfully Christians can turn to God for that security. This passage in Hebrews quotes from several encouraging passages in the Old Testament. Moses and God both encouraged Joshua as he took on a heavy new responsibility (Deuteronomy 31:6, 8; Joshua 1:5).
“I will never leave you nor forsake you: This quotation is one of the most emphatic statements in the New Testament. In Greek it contains two double negatives, similar to saying in English, ‘I will never, ever, ever forsake you’” (Nelson’s NKJV Study Bible, comment on Hebrews 13:5-6).
The second quote about God’s help allowing us to not fear comes from Psalm 118:6.