How shall I describe the luster which at that moment burst upon my vision?—C. Brockden Brown.
Second and third persons.
(2) With the SECOND AND THIRD PERSONS, shall and should are used,—
(a) To express authority, in the form of command, promise, or confident prediction. The following are examples:—
Never mind, my lad, whilst I live thou shalt never want a friend to stand by thee.—Irving.
They shall have venison to eat, and corn to hoe.—Cooper.
The sea shall crush thee; yea, the ponderous wave up the loose beach shall grind and scoop thy grave.—Thaxter.
She should not walk, he said, through the dust and heat of
the noonday;
Nay, she should ride like a queen, not plod along like a
peasant.
—Longfellow.
(b) In indirect quotations, to express the same idea that the original speaker put forth (i.e., future action); for example,—
He declares that he shall win the purse from you.—Bulwer.