Bishop Robert a prominent Hebraist and theologian, with fixed and eccentric opinions about language, wrote "A short introduction to English grammar(1762). Many schoolroom grammars in use to this day have laws of 'good usage' which can be traced directly to Bishop Lowth's idiosyncratic pronouncements as to what was 'right' and what was 'wrong'.
On page 36 he writes:
Verb To Be. Indicative mode.
1. I am, --------- We are
2. Thou art,---- Ye are 3. He is. ------ They are.
Or, 1. I be, -------- We be 2. Thou beest,-- Ye be 3. He is;(8) ----- They be.
(8)"I think it 'be thine' indeed, for thou liest in it." Shakespear, Hamlet. Be, in the singular number of this time and mode, especially in the third person, is obsolete; and is become somewhat antiquated in the plural. "A short introduction to English grammar(1762).
Is "I be" still grammatically correct?