Midrash su Salmi 12:9

R. Chelbo in the name of R. Huna said: "Whoever prays with his back turned to the synagogue is to be called wicked, as it is said (Ps. 12, 9.) On every side do the wicked walk." Abaye said: "This refers only to one who does not turn his face towards the synagogue but if he does turn his face towards the synagogue it does not matter even if his back is towards the worshipers." There was one man who prayed with his back turned to the synagogue; Elijah happened to pass by. It seemed to Elijah that the man prayed in the manner of an Arabian merchant, and he said to him: "Art thou standing before thy Master as if there were two dominions?" Thereupon Elijah drew his sword and killed the man.

R. Jochanan and R. Elazar both said: "When a man must apply for help to his fellow-men, his face changes like [the worm called] Kerum; as it is said (Ps. 12, 9.) Like a worm, so is the cheapness of the sons of men." What is Kerum? When R. Dimi came he related that among the sea-coast towns, there is a certain worm, the name of which is 'Kerum', and when the sun shines upon him, he changes into various colors. R. Ami and R. Ashi both say: "He [who has to apply for charity] is as if two judgments were passed upon him — those of fire and water, as it is said (Ps. 66, 12.) Thou hast caused man to ride on our heads; we entered into fire and into water."