“But men must know that in this theater of man's life it is reserved only for God and angels to be lookers on.”

Anonymous author; this is attributed to Mann, in The Wordsworth Dictionary of Quotations (1998) edited by Connie Robertson, and similar statements are often attributed to Thomas Paine, but the earliest published variant of such a declaration seem to be in an anecdote about an anonymous Boston woman in 1889:
I have the reputation of being of good moral character. But you know reputation is what people think of us, while character is what God and the angels know of us, and that I don't want to tell.
Anonymous Boston woman, as quoted in Current Opinion (1889)
There is a very great difference — is there not? — between the temporal and the eternal judgments, a very great difference between a man's reputation and a man's character, for reputation is what men think and say of us, while character is what God and the angels know of us.
Price Collier, in Sermons (1892)
Reputation is what men and women think of us, character is what God and the angels know of us.
Attributed to Thomas Paine in A Dictionary of Terms, Phrases,and Quotations (1895) edited by Henry Percy Smith, and Helen Kendrick Johnson
Misattributed

"Childhood".
Silex Scintillans (1655)
Context: Dear, harmless age! the short, swift span
Where weeping Virtue parts with man;
Where love without lust dwells, and bends
What way we please without self-ends. An age of mysteries! which he
Must live that would God's face see
Which angels guard, and with it play,
Angels! which foul men drive away.

1810s
Source: A Vision of the Last Judgment

Source: Billy Budd, the Sailor (1891), Ch. 19

The Rights of the Colonists (1772)

As quoted in Reader's Digest (July 1972)

Source: Paradise Lost

Religion Without God (1928). p. 90