Not afraid with any amazement (1 Peter iii. 6), introduced at the close of the marriage service in the Book of Common Prayer. The meaning is, you will be God's children so long as you do his bidding, and are not drawn aside by any distraction. No doubt St. Peter meant “by any terror of persecution.” Cranmer, being so afraid, was drawn aside from the path of duty.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894