Calvin – ‘We do not, therefore, contemplate him [Christ] outside ourselves from afar in order that his righteousness may be imputed to us but because we put on Christ and are engrafted into his body—in short, because he deigns to make us one with him.’ (Institutes 3.11.10) “It is necessary to note that Christ himself is received into the believer’s heart as well as the believer being clothed externally with his righteousness.” (Anon) We see this clearly in Galatians 3:25-4:7, clothed in righteousness, given the Holy Spirit. Not just Christ's status but Christ himself is given to us. He comes to us in his gospel. This is good news to warm the heart.
Martin Luther – “Faith does not merely mean that the soul realizes that the divine word is full of all grace, free and holy; it also unites the soul with Christ, as a bride is united with her bridegroom. From such a marriage, as St Paul says (Ephesians 5:22-32), it follows that Christ and the soul become one body, so that they hold all things in common, whether for better or worse.
This means that what Christ possesses belongs to the believing soul; and what the soul possesses, belongs to Christ. Thus Christ possesses all good things and holiness; these now belong to the soul. The soul possesses lots of vices and sin; these now belong to Christ. Here we have a happy exchange and struggle. Christ is God and a human being, who has never sinned and whose holiness is unconquerable, eternal and almighty. So he makes the sin of the believing soul is own through its wedding ring, which is faith, and acts as if he had done it [i.e. sin] himself, so that sin could be swallowed up in him. For his unconquerable righteousness is too strong for all sin, so that is made single and free from all its sins on account of its pledge , that is its faith, and can turn to the eternal righteousness of its bridegroom, Christ.
Now is not this a happy business? Christ, the rich, noble and holy bridegroom, takes in marriage this poor, contemptible and sinful little prostitute, takes away all her evil, and bestows all his goodness upon her! It is no longer possible for sin to overwhelm her, for she is now found in Christ and is swallowed up by him, so that she possesses a rich righteousness in her bridegroom.”
From Luther, Freedom of the Christian
This faith which “takes hold of this treasure, Jesus Christ” - clothed with him, given him into our hearts.