If you show favoritism you commit a sin and are convicted under the law as a transgressor.
For whoever keeps the whole law and yet offends in one point is guilty of breaking it all.
James 2:9-10
Therefore, whoever breaks one of these least commandments and teaches others to do the same shall be called the least in the Kingdom of Heaven: But whosoever shall do and teach them all shall be called great in the Kingdom of Heaven.
Matt 5:19
Archives @ Scripture-Study.org