Tobias brought the angel to his father, who greeted him, saying: "May joy be with you always." To which he replied: "What joy will there be for me, who sit in darkness and do not see the light of heaven?" He said, "Be of strong spirit, it is near that you will be healed by the Lord." And our Lord, through the miracles he performed in the flesh, showed the people of the Jews, from whom he had taken flesh, that he himself is the Son of God, and the angel, that is, the messenger of the Father's will. To whom he also proclaimed the joy of eternal salvation, saying: "Repent, for the kingdom of heaven is at hand" (Matt. III). And to those despairing of acquiring the heavenly light: "I am," he said, "the light of the world; he who follows me will not walk in darkness but will have the light of life" (John VIII).
Source: Commentary on Tobit