Albert Barnes Commentary Mark 1:40-44

"And there cometh to him a leper, beseeching him, and kneeling down to him, and saying unto him, If thou wilt, thou canst make me clean. And being moved with compassion, he stretched forth his hand, and touched him, and saith unto him, I will; be thou made clean. And straightway the leprosy departed from him, and he was made clean. And he strictly charged him, and straightway sent him out, and saith unto him, See thou say nothing to any man: but go show thyself to the priest, and offer for thy cleansing the things which Moses commanded, for a testimony unto them." — Mark 1:40-44 (ASV)

And there came a leper, etc. (Matthew 8:1). See also the commentary on Matthew 8:1.

Kneeling down to him. He knelt and inclined his face to the ground as a token of deep humiliation and earnest entreaty. Compare Luke 5:12.

If thou wilt. This showed an acknowledgment of the almighty power of Jesus and an appeal to his benevolence.

Make me clean. He meant: You can heal me of this loathsome and offensive disease—a disease justly regarded as unclean in the eye of the law—and render me legally clean, and restore me to the privileges of the congregation.

And Jesus—touched him. By the law, it was considered unclean to touch a leprous man. See Numbers 5:2. The fact that Jesus touched him was evidence that the requisite power had already been put forth to heal him and that Jesus regarded him as already clean.

I will. This was a most manifest proof of his Divine power. Only God can work a miracle. Yet Jesus did it by his own will—by an exertion of his own power. He was, therefore, Divine.

See thou say nothing to any man. The law of Moses required that the man who was healed of leprosy should be pronounced clean by the priest before he could be admitted again to the privileges of the congregation (Leviticus 19:1 and following). Christ, though he had cleansed him, yet required him to be obedient to the law of the land: to go at once to the priest and not to delay by stopping to converse about his being healed. It was also possible that if he did not go at once, evil-minded men might go before him and prejudice the priest, preventing him from declaring the healing to be thorough because it was done by Jesus. Furthermore, it was important that the priest pronounce it a genuine cure, so there might be no objections among the Jews against it being a real miracle.

Offer—those things, etc. These included two birds, cedarwood, scarlet, and hyssop. And after eight days, two male lambs without blemish, one ewe lamb, fine flour, and oil (Leviticus 14:4, 10).

For a testimony unto them. This was not a testimony to the priest, but to the people, so that they might have evidence that it was a real cure. The priest's testimony on the subject would be decisive.