Genesis 6:4-5 NIV

4 The Nephilim1 were on the earth in those days--and also afterward--when the sons of God went to the daughters of men2 and had children by them. They were the heroes of old, men of renown.3

References for Genesis 6:4

      5 The LORD saw how great man's wickedness on the earth had become,4 and that every inclination of the thoughts of his heart was only evil all the time.5

      References for Genesis 6:5