Charles H. Spurgeon on Psalms 41:9

Which did eat of my beard. If the same sentiment prevailed among the Hebrews, which prevails at the present day among the Bedouin Arabs, of sacred regard to the person and property of one with whom they have eaten bread and salt, the language is very forcible. Hath lifted up his heel: a metaphor drawn from the horse, which attacks with its heel. This language may well have been used by our Saviour, in Joh 13:18, in the way of rhetorical illustration or emphasis. George R. Noyes, D.D.