John Lightfoot on Luke 22:44

[His sweat was as it were great drops of blood.] Diodorus Siculus, speaking of a country where Alexander the Great had to do with Porus, hath this passage; "There are serpents there which, by their bites would occasion most bitter deaths: they are horrible pains that afflict any that are struck by them, and an issue of sweat, like blood, seizeth them." I would ascribe this bloody sweat of our Saviour to the bite of that old serpent, rather than to the apprehension of divine wrath.

[For more info, please see Appendix VII: Heart Rupture: A Possible Cause of the Lord's Death? by Arthur C. Custance.]