From the Christian Scriptures
(New Testament)

John 7:24:
"Judge not according to the appearance, but judge righteous judgment."

This is a command from Jesus that we stop judging people according to their mere appearances and go deeper. This might be interpreted as accepting a transsexual's perceived gender identity instead of concentrating solely on their genetic gender.
 

1 Corinthians 6:18-20:
"... know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?  For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's.

Some who oppose gender transitioning interpret this passage as requiring a person to accept both their body (including their genetic gender) and spirit (including their gender identity) as creations of God. Thus a transgender individual should accept their conflicts over gender without resorting to hormone treatments and/or gender reassignment surgery.
 

1 Corinthians 11:14:
"Doth not even nature itself teach you, that, if a man have long hair, it is a shame unto him?"

If you believe that a person's gender is defined by their gender identity, then this passage does not pose a problem for MTF transgender persons. She would be considered a woman and thus expected to wear long hair. However most religious conservatives believe that genetic gender rules; a MTF transsexual remains a male; long hair would have been a disgrace in Paul's culture. This verse may or may not be applicable in today's culture, depending upon how culture-bound you interpret the passage to be.
 

2 Timothy 3:2-4:
"For men shall be ... unholy, without natural affection, ... incontinent... lovers of pleasures more than lovers of God."

The meaning of "incontinence" has changed since 1611 CE when the King James Version was translated. A better translation today is "without self-control."

Some religious conservatives have used this verse to condemn transgender persons. For example, the former ignore the female gender identity of a heterosexual MTF transgender individual and consider them to be a male. Since the individual is probably sexually attracted to men, many social and religious conservatives would regard the person's behavior to be homosexual, hedonistic, and without natural affection or self control.