That which is itself unclean makes whatever it touches unclean also.
So in the moral sphere, "evil communications corrupt good manners" (1 Corinthians 15:33), and "a little leaven leaveneth the whole lump" (1 Corinthians 5:6), and so with respect to the spread of heresy, "Their word will eat as doth a canker (or gangrene)" (2 Timothy 2:17).
On the other hand, that which is itself holy makes that which it touches to be holy (Leviticus 6:18). Therefore, when the Holy One was on the earth, "the whole multitude sought to touch him: for there went virtue out of him, and healed them" (Luke 6:19); and they "brought unto him all that were diseased; and besought him that they might only touch the hem of his garment: and as many as touched were made perfectly whole" (Matthew 14:1-36:85, 36). Thus the woman with an issue of blood "came behind him, and touched the border of his garment: and immediately her issue of blood stanched.… And when the woman saw that she was not hid, she came trembling, and falling down before him, she declared unto him before all the people for what cause she had touched him, and how she was healed immediately" (Luke 8:44-47). Hence, when mankind had fallen in Adam, for the restoration of the race a new Head was found in Christ Jesus, into whom each person is baptized, and by a mystical contact with whom he may be sanctified.