"Jesus spat on the ground and made some mud with the spittle; he rubbed the mud on the man's eyes and said, “Go and wash your face in the Pool of Siloam.” (This name means “Sent”.) So the man went, washed his face, and came back seeing."

(John 9.6-7 GNB)

Jesus used mud. Not olive oil (James 5.14), but mud (and saliva).

Jesus did not need to use anything; he could just say it, and the man would be healed. But he did not.

And the man did not immediately see, either. He had to apply his "faith" by going to the Pool of Sent and washed his face. Only then was he able to see.

If he did not believe, he would not do what Jesus told him to do. And if he did not wash his face at the pool, he would not see.

Jesus can use mud still, today, to do miracles. As long as I have faith.