Lying is a heinous sin, and hypocrisy is its firstborn daughter. When someone thinks something in his heart, or teaches it, but at the same time speaks contrarily, pretending kindness and compassion toward his enemy whom he intends to destroy, he commits the mother of all sins. And when a man pretends to be solicitous toward God about his commandments, showing devised holiness, but remains within himself impure, deceitful, and lover of money, he certainly falls into the condemnation of God. The believer has also to beware of hypocrisy lest he believes within himself and denies his Lord with his mouth, saying as Peter said in his temptation, "I do not know this man."
So beware of hypocrisy, for all your concealed thoughts, backbiting whisperings, and aggressive acts will certainly appear on the Last Day, and sometimes in this world. At that time you will die of shame, for over all, it will appear that your hypocrisy affected others and made them fall as an infectious microbe. Hypocrisy enters into all areas of life, as a leaven leavens the whole lump. A hypocrite does not only hurt himself, but also hurts others. He hurts the whole society, and partakes of allowing all to fall, contrary to his reformative and righteous appearance.