John 9:6

Verse 6. And made clay, &c. Two reasons may be assigned for making this clay, and anointing the eyes with it. One is, that the Jews regarded spittle as medicinal to the eyes when diseased, and that they forbade the use of medicines on the Sabbath. They regarded the Sabbath so strictly that they considered the preparation and use of medicines as contrary to the law. Especially it was particularly forbidden among them to use spittle on that day to heal diseased eyes. See instances in Lightfoot. Jesus, therefore, by making this spittle, showed them that their manner of keeping the day was superstitious, and that he dared to do a thing which they esteemed unlawful.