Tertullian, Against Marcion 4.28

No wonder He takes no pleasure in the hypocrisy of the Pharisees — people who honor God with their lips while their hearts are far from Him. "Watch out for the leaven of the Pharisees," He tells His disciples, "which is hypocrisy," not the preaching of the Creator (Matt. 16:6). The Son hates the stubborn; He refuses to let His own become like that toward Him — not toward someone else — toward the very One in whom hypocrisy took root and was tolerated, the One whose example the disciples were warned to avoid. So, when He forbids the Pharisees' example, He is forbidding that same corruption from taking hold in Him, the very One in whom the Pharisees indulged it. Because He has condemned their hypocrisy — a mask that hides the heart's secrets and unbelief behind superficial duties, a mask that holds the key of knowledge yet neither enters itself nor lets others in — He adds: "Nothing is covered that will not be uncovered, and nothing hidden that will not be known" (Matt. 10:26). He says this so no one imagines He is staging some backward, covert revelation of an unknown God. After all, He drags into the open even the things they muttered among themselves or debated in private — specifically, their talk about Him: "He casts out demons only by Beelzebul" (Matt. 12:24) — words destined to become public knowledge and on everyone's lips through the proclamation of the Gospel.