Judges 14:3

Then his father and his mother said unto him, Is there never a woman among the daughters of thy brethren, of his own tribe, or among all my people, in all Israel, that thou goest to take a wife of the uncircumcised Philistines, for the rite of circumcision was a distinction which Israel had above all heathen nations as a sign of God's covenant. The objection of Manoah and his wife was founded upon Exodus 34:16 and Deuteronomy 7:3, for, although the philistines are not expressly named in the list of heathen nations with whose members marriage was not to be consummated, yet the principle of the prohibition excluded the Philistines as well as all others. Mixed marriages are dangerous at all times, and parents will best perform their duty if they prevent the union between their children and unbelievers, and also false believers, from the start. And Samson said unto his father, Get her for me; for she pleaseth me well. It may have been only a temporary attachment which Samson felt, but he was insistent, and his parents finally consented.