loose his shoe: Pulling off the shoe seems to express his being degraded to the situation of slaves, who generally went barefoot; and spitting in or rather before (biphney) his face, was a mark of the utmost ignominy. Rth 4:7-8; Isa 20:2; Mar 1:7; Joh 1:27
spit: Num 12:14; Job 30:10; Isa 50:6; Mat 26:67, Mat 27:30; Mar 10:34