Commenting on the background of the parable of the Good Samaritan, English New Testament scholar James Crossley offered the following insightful note:
The Good Samaritan (Luke 10.29-37)
Matt. 23.25-6//Luke 11.38-41 is presented as another critique of a different emphasis on purity laws but which again works with the assumption of the general validity of the biblical purity laws. As with Mark 7.1-23, the passage also makes sense in the context of early Jewish purity discussions, although there may be more tacit acceptance of the opinions of the Pharisaic opponents. Like Mark, there is an emphasis on prioritizing ‘moral’ purity, as in the contrast between ‘inner’ and ‘outer’ moral purity, imagery used and implied elsewhere (e.g. Matt. 5.27-8; Matt. 6.16-18; Matt. 23.27-8). The final example—the parable of the Good Samaritan (Luke 10.29-37)—is different in that the passage most likely concerns issues surrounding corpse impurity but the overall attitude towards purity is similar to Mark 7.1-23 and Matt 23.25-6//Luke 11.38-41.
The Lukan parable gives us a clue about the importance of corpse impurity in that the person is ‘half-dead’ and the characters are judged over whether they will risk touching him. In the case of the priest, the passage has been assessed in terms of a stark contrast with the priestly commandment in Lev. 21.1-3:
The Lord said to Moses: Speak to the priests, the sons of Aaron, and say to them: No one shall defile himself for a dead person among his relatives/people (בעמיו), except or his nearest kin: his mother, his father, his son, his daughter, his brother; likewise, for a virgin sister, close to him because she has had no husband, he may defile himself for her.
Yet Lev. 21.1-3 is actually an important passage in early Jewish law in Palestine for the discussion of dealing with an abandoned corpse, and Luke 10.29-37 fits in with these sorts of debates, as well as with debates over the interpretation of purity laws outside the Temple. For a start, Lev. 21.1-3 does not mention any serious punishment for transgression which stands in contrast to the rest of Lev. 21, though an impure priest would not be able to serve in the Temple (cf. Ezek. 44.25-7). There are presumably practical reasons for this lack of punishment as it is not difficult to imagine priests contracting impurity unwittingly (Lev. 5.3) and there appears to have been attempts to prevent the possibility of unwittingly contracting corpse impurity (e.g. Luke 11.44//Matt. 23.27). The case of the Nazirite (Num. 6) provides an important analogy in that we have people who were dedicated to strict observance of purity laws yet the possibilities of contracting corpse impurity were known. The Nazirite should not contract corpse impurity even from close relatives but Num. 6 raises the possibility that a nearby person might suddenly die. If this is the case, head-shaving and offerings are required of the Nazirite (Num. 6.9-12). There is also a crucial qualification mentioned in Lev. 21.1, namely that a priest should not contract corpse impurity when ‘among his relatives/people’, which links to the issue of what to do with an unattended corpse in the countryside. In the case of the parable of the Good Samaritan, there is already a potential exemption for the priest as he is not among his people. The reason for an abandoned corpse being problematic is found in Num. 19.16: ‘Whoever in the open field touches one, who has been killed by a sword or who has died, or a human bone, or a grave, will be unclean seven days.’ These texts for the general legal context for the debate attributed to the late first century between R. Eliezer b. Hyrcanus and the Sages have clear similarities with the parable of the Good Samaritan (m. Nazir 7.1). They debate whether there should be exemptions in the case of the Nazirite and the high priest when faced with an unattended corpse:
A high priest and a Nazir do not contract corpse uncleanness on account of [burying even] their close relatives. But they do contract corpse uncleanness on account of a neglected corpse. [If] they were going along the way and found a neglected corpse—R. Eliezer says, ‘Let a high priest contract corpse uncleanness, but let a Nazir not contract corpse uncleanness.’ And the Sages say, ‘Let a Nazir contract corpse uncleanness, but let a high priest not contract corpse uncleanness.’ (m. Nazir 7.1; cf. Num. 6.1-12; Lev. 21.11-12; Spec. Leg. 1.113-15, 250)
The passage obviously discusses the case of the high priest but clearly someone like R. Eliezer would have likely agreed with the sentiment in the parable of the Good Samaritan that the priest should have been prepared to contract corpse impurity in such circumstances.
Luke 10.29-37 provides some important further details. Keeping in mind the sharp descent from Jerusalem (War 4.452-3), the priest and the Levite are not presented as about to serve in the Temple. On the contrary: ‘Now by chance a priest was doing down (κατεβαινεν) that road; and when he saw him, he passed by on the other side. So likewise a Levite . . . ‘ (Luke 10.31-2). Nor was the person who had been attacked en route to the Temple. They too were ‘going down’ (κατεβαινεν) from Jerusalem to Jericho’ (Luke 10.30). This means that we should not be locating the debate an overriding of Lev. 21.1-3 because the action would then be taking place upwards and towards the Temple. Rather, the debate is about the interpretation and expansion of purity law outside the Temple and is very much akin to the debate in m. Nazir 7.1. This also illuminates the choice of the Samaritan. This is not, as if often romantically pointed out, the ‘subversive’ or ‘shocking’ expansion of Jewish boundaries to include so-called ‘despised’ outsiders. What works better in the context of legal disputes is the construction of Samaritans as people known to have the Pentateuch as their text and deemed to be very similar to the Sadducees in this respect (cf. m. Sheh. 8.10; b. Qidd. 75b; and m. Nidd. 4.2, ‘The daughters of the Sadducees, if they follow the ways of their fathers, are deemed like to the women of the Samaritans’). With the Lukan Jesus and the scribe prioritizing the Shema’ (Deut. 6.5) and loving the neighbour (Lev. 19.18), the presentation is once again that of ‘commandments’ in tension with ‘tradition’, as we saw more explicitly in Mark 7.1-23. (James G. Crossley, Jesus and the Chaos of History: Redirecting the Life of the Historical Jesus [Oxford: Oxford University Press, 2015], 119-21, italics in original, emphasis in bold added)