Thomas Aquinas

“ For though insensible creatures are not capable of being venerated for their own sake, yet the rational creature is capable of being venerated for its own sake. Consequently the worship of "latria" is not due to any mere rational creature for its own sake. Since, therefore, the Blessed Virgin is a mere rational creature, the worship of "latria" is not due to her, but only that of "dulia": but in a higher degree than to other creatures, inasmuch as she is the Mother of God. ”

“ The dead body of a saint is not identical with that which the saint had during life, on account of the difference of form, viz. the soul: but it is the same by identity of matter, which is destined to be reunited to its form. ”

“ The cross, considered in itself, is not an object of veneration, as stated above ( [4122] AA [4] ,5) . But the Blessed Virgin is in herself an object of veneration. Hence there is no comparison.
Art. 6 - Whether any kind of worship is due to the relics of the saints? Objection 1: It would seem that the relics of the saints are not to be worshiped at all. For we should avoid doing what may be the occasion of error. But to worship the relics of the dead seems to savor of the error of the Gentiles, who gave honor to dead men. ”

“ If anyone dare to say that the man assumed should be adored besides the Divine Word, as though these were distinct persons; and does not rather honor the Emmanuel with one single adoration, inasmuch as the Word was made flesh ”

“ It is clear from this that he who has a certain affection for anyone, venerates whatever of his is left after his death, not only his body and the parts thereof, but even external things, such as his clothes, and such like. Now it is manifest that we should show honor to the saints of God, as being members of Christ, the children and friends of God, and our intercessors. ”

“ If a father's coat or ring, or anything else of that kind, is so much more cherished by his children, as love for one's parents is greater, in no way are the bodies themselves to be despised, which are much more intimately and closely united to us than any garment ”