Exodus 29:19-20

Now the ear of the high priest is anointed so the priest might be truly attuned to God’s Word and the appeals of the people. His ears are tuned into really listening and discerning, so that he can get to the heart of a matter and be able to rightly counsel people because he hears beyond the mere words; and because he has been listening to God, he has discernment, and he has God’s Word with which to counsel.

The ear is very important to a priest, and God emphasized this by consecrating the ear, by anointing it with the blood, and just reminding the priest forever to not forget the importance of listening to people.

Now it is very likely that anointing the thumb was a reference to make sure that you are handling your responsibilities the way a priest needs to handle them, in a consecrated way. Remember they always had to handle the sacrifices. They had to handle the furniture in the tabernacle.

What about anointing the toe—the great toe? It was to remind them that they are to be an example before the people and their walk before the people better be upright and holy.

So their walk, the way they did their work, and the way they listened to both God and the people—and so God reminded them by anointing each vital part of their responsibilities that would keep them attuned to carrying out their responsibilities in a holy way.