Tares

tares [TAIRS]
n. an unwelcome or objectional element

[From Arabic ṭarḥah ("rejection, subtraction") from ṭaraḥa ("to throw away")]

In a literal sense, tares are weeds, especially vetches. However, the Christian Bible uses tares figuratively to mean an undesirable element, such as a servant of the devil.

In Matthew 13, Jesus takes the stage on the deck of a ship at harbor and entertains "the whole multitude" on shore. He warms up the crowd with his classic yarn about weeds and wheat-farming (Matthew 13:25-30):

But while men slept, his enemy came and sowed tares among the wheat, and went his way. But when the blade was sprung up, and brought forth fruit, then appeared the tares also. So the servants of the householder came and said unto him, Sir, didst not thou sow good seed in thy field? from whence then hath it tares? He said unto them, An enemy hath done this. The servants said unto him, Wilt thou then that we go and gather them up? But he said, Nay; lest while ye gather up the tares, ye root up also the wheat with them. Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.

The implication is that the bad seeds, the tares, will eventually burn in Hell, even if they don't get punished immediately. The day of reckoning comes for all. In the meantime, just because there are bad seeds among you, God does not recommend mankind punishing everyone to root out the wicked. For those in his audience too dense to understand, Jesus explained his parable:

The field is the world; the good seed are the children of the kingdom; but the tares are the children of the wicked one; The enemy that sowed them is the devil; the harvest is the end of the world; and the reapers are the angels. As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world. The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity; And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth.