Rom 10:8

“True knowledge, then, consists in the understanding of Christ, which Paul terms the wisdom of God hidden in a mystery, which "the natural man receiveth not," the doctrine of the cross; of which if any man "taste," he will not accede to the disputations and quibbles of proud and puffed-up men, who go into matters of which they have no perception. For the truth is unsophisticated; and "the word is nigh thee, in thy mouth and in thy heart," as the same apostle declares, being easy of comprehension to those who are obedient. For it renders us like to Christ, if we experience "the power of his resurrection and the fellowship of His sufferings." For this is the affinity of the apostolical teaching and the most holy "faith delivered unto us," which the unlearned receive, and those of slender knowledge have taught, not "giving heed to endless genealogies," but studying rather [to observe] a straightforward course of life; lest, having been deprived of the Divine Spirit, they fail to attain to the kingdom of heaven. For truly the first thing is to deny one's self and to follow Christ; and those who do this are borne onward to perfection, having fulfilled all their Teacher's will, becoming sons of God by spiritual regeneration, and heirs of the kingdom of heaven; those who seek which first shall not be forsaken.”

“Here we have to bear in mind the important distinction between what is possible in theory and what is realized in practice.… Christ, who is the Word of God, is potentially near us and near everyone, but this is only realized in practice when I confess with my mouth that Christ is Lord and when I believe in my heart that God has raised him from the dead.”

“Moreover, we hear both also preaching, in the first place, not only repentance, but the kingdom of heaven, which, as we have learned, is within us; for the word which we believe is near us, in our mouth, and in our heart; which they, being put in remembrance of, will learn to confess with their mouths that Jesus is the Christ; believing in their heart that God hath raised him from the dead, and being as those who hear, that "with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation."”

“Then when he says, but says the Scripture, he shows the fruit of faith on the same authority. First, he quotes the authority; second, he explains, at this is the word of faith; third, he proves that the explanation is fitting, at believe in your heart. First, therefore he says: but says the Scripture? It says this: the word is near you, even on your mouth and in your heart. For this is what follows after the aforementioned words in Deuteronomy: the word is very near you, in your mouth and in your heart (Deut 30:14). As if to say: do not suppose that you are lacking the word of justifying faith, just because Christ is in heaven according to his divine nature and descended into hell after the death of his human nature. For in descending from heaven and rising from the dead, he impressed the word of faith on your lips and in your heart. Hence the statement that the word is near you can be referred to the fact that we have obtained God's word through Christ's birth and resurrection: it was declared at first by the Lord (Heb 2:3); behold, I have given my words in your mouth (Jer 1:9). Or, according to the Gloss, the word near should be understood with reference to usefulness, as we say something is near us when it is expedient or useful to us. For our heart is cleansed by the word of God: now you are clean because of the word which I have spoken to you (John 15:3). Or it can be referred to the fact that the words of faith, even though they are above reason—many things are shown to you above the understanding of men (Sir 3:25)—are nevertheless not contrary to reason, because truth cannot be contrary to truth. Your decrees are very sure (Ps 93:5).”