No one who has been emasculated by crushing or cutting may enter the assembly of the LORD. (Deut 23.1, NASB)
This is rarely used as a proof text, but when it does it is used to mean that a male who undergoes SRS is not welcomed by the Lord. Perhaps its lack of usage is because Christians would have to equally condemn anyone whose penis was "crushed" accidentally. The EV Alliance Report, which strongly condemns SRS, recognizes this verse itself does not condemn SRS.
To leap to such conclusions, however, can result in misuse of the Bible and a failure to do justice to the complexities of responsible exegesis and application. For a start, in relation to Deuteronomy 23:1, there is a clear progression in Scripture which culminates in the implied acceptance of the genitally-mutilated by Jesus in Matthew 19:12 and the conversion, baptism, and acceptance into the Kingdom of God of the Ethiopian eunuch in Acts 8:26-39.1 [Footnote] 1. Also most commentators accept that Isaiah 56:4-5 removes the ban on the genetically mutilated being admitted to the "assembly of the Lord." (p46)
Sex Reassignment Surgery and Deuteronomy 23:2 (23:1) A rabbi's analysis and application to SRS.