E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Forty Stripes save One.
The Jews were forbidden by the Mosaic law to inflict more than forty stripes on an offender, and for fear of breaking the law they stopped short of the number. If the scourge contained three lashes, thirteen strokes would equal forty save one.
Forty stripes save one. The thirty-nine articles of the Anglican Church.