‘ Now this was the custom in former time in Israel concerning redeeming and concerning exchanging. To confirm all things, a man drew off his shoe, and gave it to his neighbour, and this was the manner of attestation in Israel.'
The writer then pauses in order to explain an ancient custom, which presumably in his day had ceased to apply, so as to explain what happened next (Ruth 4:8). Where a man refused to act as kinsman redeemer (to act ‘concerning redeeming and concerning exchanging') he evidenced it by publicly taking off his shoe and handing it over to the one on whom he devolved the right. This was final confirmation in the sight of witnesses that he had withdrawn his own right to act as kinsman redeemer, and had passed it on to his neighbour.
This custom may be connected with the fact that it was the shoe which trod on the land denoting the owner's possession. Compare YHWH's words to Abraham in Genesis 13:17, and His words to Joshua in Joshua 1:3. The result being that the handing over of the shoe was seen as devolving possession. But it was also perhaps an adaptation of the original Law. For in the Law of Moses, where a person refused to act as kinsman and beget children through the wife of a deceased relative in order to preserve the name of her family, the wife had the right to loose his shoe and spit in his face (Deuteronomy 25:9), and his family would from then on be known as ‘the family of him who had had his shoe loosed' (Deuteronomy 25:10). By this he would be ‘branded' as having failed to fulfil his responsibility towards his wider family. It may be that the custom had now been altered in order to make it less openly offensive. If this is the case it was seemingly mainly followed in the time of the Judges, whilst no longer being so in the time of David. That would not, however, lessen the continual importance of the law of Levirate marriage.