Cast your burden on the LORD,
and he will sustain you. —Psalm 55:22
The word translated "burden" only occurs here in this form in the Old Testament and means an allotment or "that which is given." (The noun means “a gift.") This is the portion God gives us each day, the circumstances in which we find ourselves.
This is the text that lies behind Peter’s oft-quoted words: ”Casting all your care upon Him, because He cares for you" (1Peter 5:7).
Peter's Bible, The Septuagint, translated "burden" as merimna, "cares," referring, by metonymy, to the uncertainties and anxieties that grow out of the burdens we bear: The worry of a hard marriage, the sorrow of a difficult child, the strain of a broken relationship, the pain of an aging body, the care of an elderly parent, the nagging weight of an intransigent congregation—this may be our portion.
But, the poet assures us, if, by prayer, we cast our burdens on the Lord He will sustain us. Interesting. He does not promise that He will take our circumstances away, for they may be ours for a lifetime. But He will sustain us in our circumstances, giving us grace for every hour. He will “strengthen and help (us) and cause (us) to stand, upheld by His righteous, omnipotent hand!”
“As your days so shall your strength be” (Deuteronomy 33:25).