But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
But what saith it? [it saith] - continuing the quotation from Deuteronomy 30:14,
The word is nigh thee (easily accessible), even in thy mouth - when thou confessest Him,
And in thine heart - when thou believest on Him. The thoughtful student of this passage will observe, that though it is of the law that Moses is speaking in the place quoted from, yet it is of the law as Israel shall be brought to look upon it when the Lord their God shall circumcise their heart "to love the Lord their God with all their heart," etc. (Romans 10:6); and thus, in applying it, the apostle (as Olshausen truly observes) is not merely appropriating the language of Moses, but keeping in the line of his deeper thought.
That is, the word of faith, which we preach - i:e., the word which men have to believe for salvation (compare, for the phrase, 1 Timothy 4:6).