To say that this poem or song is not religiously based is not completely correct. The concept is losely based on a couple of verses from the Sermon on the Mount in Matthew in the New Testament.
Matthew 7:1-5
1 Judge not, that ye be not judged.
2 For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again.
3 And why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?
4 Or how wilt thou say to thy brother, Let me pull out the mote out of thine eye; and, behold, a beam is in thine own eye?
5 Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye.