12 And he pours water upon the feet of Christ, who purifies his conscience from the defilement of sin, for Christ walks in the breast of each. Take heed, then, not to have your conscience polluted, and so to begin to defile the feet of Christ. Take heed lest He encounter a thorn of wickedness in you, whereby as He walks in you His heel may be wounded. For this was why the Pharisee gave no water for the feet of Christ, that he had not a soul pure from the filth of unbelief. For how could he cleanse his conscience who had not received the water of Christ? But the Church both has this water and has tears. For faith which mourns over former sins is wont to guard against fresh ones. Therefore, Simon the Pharisee, who had no water, had also, of course, no tears. For how should he have tears who had no penitence? For since he believed not in Christ he had no tears. For if he had had them he would have washed his eyes, that he might see Christ, Whom, though he sat at meat with Him, he saw not. For had he seen Him, he would not have doubted of His power.
Source: Letters (New Advent)