Jamieson, Fausset and Brown on Luke 10:31-32

31-32. came down a ... priest ... and a Levite--Jericho, the second city of Judea, was a city of the priests and Levites, and thousands of them lived there. The two here mentioned are supposed, apparently, to be returning from temple duties, but they had not learnt what that meaneth, 'I will have mercy and not sacrifice' [Trench].

saw him--It was not inadvertently that he acted.

came and looked--a further aggravation.

passed by--although the law expressly required the opposite treatment even of the beast not only of their brethren, but of their enemy (De 22:4; Ex 23:4, 5; compare Is 58:7).