Does the Marriage of an Unbeliever to a Believer Sanctify the Unbeliever?

“What did Paul mean in 1 Corinthians 7:14 when he said that an unbeliever is ‘sanctified’ by a Christian spouse?”

First, the Bible student must understand the meaning of the term “sanctified,” and the various uses of that term that are made by the sacred writers of the New Testament.

The word appears in two grammatical forms in the New Testament. The noun is hagiasmos; it is found 10 times in the New Testament and is rendered by the English terms “holiness” and “sanctification” (cf. Romans 6:19,22; 1 Corinthians 1:30; 1 Thessalonians 4:3-4, KJV). The verb is hagiazo. It occurs 29 times in the New Testament and is found in the KJV as “sanctify” (Matthew 23:17,19), “hallow” (Matthew 6:9), and “be holy” (Revelation 22:11). [Note: Kindred terms from the same stem appear as “holy,” “holiness,” “sanctuary,” “saint,” etc.]

Basically, to be “sanctified,” carries the idea of “having been separated from (something), set apart.” In classical Greek the concept was that of something “sacred” that is not accessible to the general public. Herodotus wrote concerning a “sacred grove of plane-trees” where a certain deity was worshipped only by the Carians (History, 5.119), i.e., it was a segregated, separated area.

Both God the Father and Christ the Son are to be sanctified (Numbers 20:12; 27:14; 1 Peter 3:15), which means they are to be “set apart” (cf. Matthew 6:9) as unique and authoritative Sovereigns over our lives. Deity is a class all its own.
God sanctifies (sets apart as holy) those who respond to his truth (John 17:17) in obedience to the gospel. One is sanctified when he is cleansed, which occurs when his faith leads him to demonstrate the death and resurrection of Christ in the washing of water (i.e., burial in water—Romans 6:3-4; Colossians 2:12) by means of the instruction of “the word” (Ephesians 5:26; 1 Corinthians 6:11). The “water” is an allusion to baptism, as virtually all scholars concede.
There is a sense in which man sanctifies himself by exercising his power of choice in yielding to the will of God (Leviticus 11:44; 1 Peter 1:15).
The foundational basis of spiritual sanctification is the death of Christ (Hebrews 9:13-14; 10:10).
Now, to the question at hand. Occasionally “sanctified” takes on a special sense. For example, Paul declares that the unbeliever who is married to a Christian is “sanctified” by the believer (1 Corinthians 7:14).

This does not mean that the marriage itself saves the non-Christian. If that were the case, the apostle would not refer to the union as that of a “believer” and an “unbeliever.” Moreover, this idea would contradict numerous passages that reveal salvation must be accessed by personal obedience (Acts 2:40; 2 Thessalonians 1:7-9; Hebrews 5:8-9).

Rather, the sense seems to be that the unbeliever, being in close proximity with the Christian spouse, is in a sort of “set apart” environment—cut off from the total and extreme godless influence of the world. The end result is the happy possibility that the sinner may be won to the Lord through Christian influence.

W.E. Vine observed that “the unbelieving husband or wife is relatively set apart through his or her believing partner, and abiding in the natural union instead of breaking it by leaving, receives a spiritual influence holding the possibility of actual conversion” (1st Corinthians—Local Church Problems, Grand Rapids: Zondervan, 1951, p. 97—emp. WJ).

This is a reasonable explanation that does not conflict with scripture elsewhere.

http://www.christiancourier.com/articles/print/does_the_marriage
_of_an_unbeliever_to_a_believer_sanctify_the_unbeliever