Matthew 7:16 – 20
New International Version (NIV1984)
16 By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles? 17 Likewise every good tree bears good fruit, but a bad tree bears bad fruit. 18 A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 Thus, by their fruit you will recognize them.
From BibleGateway.com: http://www.biblegateway.com/passage/?search=Matthew 7:16 – 20&version=NIV1984