Lord, I am not worthy that you should enter under my roof, Mt 8:8Just as the priest's exhortation is scriptural, the response is as well. It comes from the encounter between Jesus and the centurion found in Matthew 8. Our response is based on the response of the centurion to Jesus' recommendation that He should go to the centurion's house to heal the man's paralyzed servant.
but only say the word and my soul shall be healed.
As [Jesus] entered Capernaum, a centurion came forward to him, begging him and saying, “Lord, my servant is lying paralyzed at home, in terrible distress.” And he said to him, “I will come and heal him.” But the centurion answered him, “Lord, I am not worthy to have you come under my roof; but only say the word, and my servant will be healed. For I am a man under authority, with soldiers under me; and I say to one, ‘Go,’ and he goes, and to another, ‘Come,’ and he comes, and to my slave, ‘Do this,’ and he does it.” [...] Jesus said, “Go; let it be done for you as you have believed.” And the servant was healed at that very moment. (Mt 8:5-13)Whereas the old translation used the phrase “not worthy to receive you”, the new translation is more literal: “not worthy that you should enter under my roof”. By this, the centurion meant that Jesus should not enter his house (be received, like a guest). When we use the word “roof” here, though, we should not think we are talking about the roof of our mouths.
What roof do we mean? We are temples of the Holy Spirit, and our flesh is like the “roof” of this temple. We know we are unworthy to be such temples, where God is present spiritually; we are even less worthy to receive our Lord in the Blessed Sacrament. But here Christ does for us what He did not do for the centurion, not because our faith is any less (although oftentimes it is), but because “God had foreseen something better for us.” (Heb 11:40) Jesus gladly comes to us in the Eucharist.