He shall cover thee with his feathers, and under his wings shalt thou trust: his truth shall be thy shield and buckler. – Psalm 91:4
From Wikipedia:
…shall is used with the meaning of obligation, and will with the meaning of desire or intention.
Shall is a word used by lawyers to create obligations in business contracts.
Where “will” can be a common, plain expression of desire for the future, Shall is serious, unemotional and business-like in its statement of future debts and obligations that are to be fulfilled.
God shall cover thee with His feathers…
It’s a promise that is even more true for you under the New Covenant.
God always keeps His promises…all that remains is for you to claim them by faith.