As the Lord came down from the mountain, the multitudes met Him, because they were unable to ascend to the heights. And the first to meet Him was a leper.  Because of his leprosy he had been unable to hear the wondrous discourse of the Savior spoken on the mountain. And observe that he was the first to be miraculously cured; then, secondly, the servant of the Centurion; thirdly the mother-in-law of St. Peter, of a fever, in Capharnaum; in the fourth place, those that were brought to Him possessed with devils, whose evils spirits He cast forth with His word, when all that were sick He healed.  Fittingly, after His sermon and instruction, an occassion presents itself for a sign, so that the sermon they had heard might be confirmed by the power of a miracle.
Lord if thou wilt, thou canst make me clean. He who petitions the will of the Lord, does not doubt His power. And Jesus stretching forth His Hand, etc., etc. Stretching forth His Hand, immediately the leprosy disappears. Consider here again how humble and unassuming the answer. The leper had said: if thou wilt. The Lord answers: I will. The leper had already said: thou canst make me clean. The Lord joins both requests, and says: be thou made clean.  
Not therefore, as many Latins are of opinion, must we unite and read together these phrases, as: I will be thou made clean; but separately, as that He first says: I will, Then, as it were commanding, He says:  Be thou made clean.