These brief notes are from a study I did of this parable of Jesus which brought to light the reasons why the priest and Levite did not stop to help the wounded man. The Law of Moses was a large barrier to their rendering him assistance, although of course one cannot rule out a lack of compassion for their brother in need as a contributing factor.
Luke 10:25 (KJV) And, behold, a certain lawyer stood up, and tempted him, saying, Master, what shall I do to inherit eternal life?
26 He said unto him, What is written in the law? how readest thou?
27 And he answering said, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself.
28 And he said unto him, Thou hast answered right: this do, and thou shalt live.
29 But he, willing to justify himself, said unto Jesus, And who is my neighbour?
30 And Jesus answering said, A certain man went down from Jerusalem to Jericho, and fell among thieves, which stripped him of his raiment, and wounded him, and departed, leaving him half dead.
Notice how Jesus' story engages his hearers from start to finish: they would have intellectually jousted with it and found justifications for the priest and the Levite until the introduction of the Samaritan and the final devastating question at 10:36.
31 And by chance there came down a certain priest that way: and when he saw him, he passed by on the other side.
Strictly speaking, this priest was simply following Mosaic law in not defiling himself--see Lev. 21:1--and not doing this to be deliberately inhumane. By this detail, Christ shows us that "the letter killeth, but the spirit giveth life" (2 Cor. 3:6).
32 And likewise a Levite, when he was at the place, came and looked on him, and passed by on the other side.
The Levite could have stopped, albeit at some inconvenience to himself. If the man were dead, the Levite would be unclean for seven days--see Num. 19:11. But the law did require him to relieve his brother in need (Lev. 25:35). He "shut up his bowels of compassion" (1 Jn. 3:17) instead.
33 But a certain Samaritan, as he journeyed, came where he was: and when he saw him, he had compassion on him,
The Samaritan was an outcast (John 4:9) who was considered by the Jews to have no part in the worship of the true God. (See 2 Kings 17:27-41, John 4:20.) But even with no part in Israel's covenant, he outdoes the priest and the Levite by following the law written in his heart (Rom. 2:13-15).
34 And went to him, and bound up his wounds, pouring in oil and wine, and set him on his own beast, and brought him to an inn, and took care of him.
35 And on the morrow when he departed, he took out two pence, and gave them to the host, and said unto him, Take care of him; and whatsoever thou spendest more, when I come again, I will repay thee.
"Host"--an Elizabethan term for "innkeeper."
36 Which now of these three, thinkest thou, was neighbour unto him that fell among the thieves?
The devastating question; the Jews would feel that, if they could not outdo a Samaritan, they were in a pitiful state indeed.
37 And he said, He that shewed mercy on him. Then said Jesus unto him, Go, and do thou likewise.
The answer given is not "the Samaritan," but "He that shewed mercy on him"! This shows that the conclusion to which Jesus led His audience was not one that they were eager to make.