It is sometimes argued that the trajectory of Biblical teaching is such that some things which are permitted in the Old Testament are restricted in the New (e.g., slavery) and sometimes the Old is restrictive where the New Testament is expansive (food laws). Recently we have heard much about this with regard to same-sex marriage. It is a complicated subject.
Darrell Bock has a good post about it today.
Darrell Bock, “The Bible and Same-Sex Marriage: 6 Common but Mistaken Claims,” The Gospel Coalition (July 27, 2015) http://www.thegospelcoalition.org/article/bible-same-sex-marriage-6-wrong-trajectories