Brewer's: Ecce Signum
See it, in proof; Behold the proof!
“I am eight times thrust through the doublet, four through the hose; my buckler cut through and through; my sword hacked like a handsaw— ecce signum!” —Shakespeare: 1 Henry IV., ii. 4.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894