Objection 1. It seems that piety is not a gift. For the gifts differ from the virtues, as stated above (I-II, 68, 1). But piety is a virtue, as stated above (Question 101, Article 3). Therefore piety is not a gift.
Objection 2. Further, the gifts are more excellent than the virtues, above all the moral virtues, as above (I-II, 68, 8). Now among the parts of justice religion is greater than piety. Therefore if any part of justice is to be accounted a gift, it seems that religion should be a gift rather than piety.
Objection 3. Further, the gifts and their acts remain in heaven, as stated above (I-II, 68, 6). But the act of piety cannot remain in heaven: for Gregory says (Moral. i) that "piety fills the inmost recesses of the heart with works of mercy": and so there will be no piety in heaven since there will be no unhappiness [Cf. 30, 1]. Therefore piety is not a gift.
On the contrary, It is reckoned among the gifts in Isaiah 11:2 [Douay: 'godliness'] ["Pietas," whence our English word "pity," which is the same as mercy.]
I answer that, As stated above (I-II, 68, 1; I-II, 69, 1,3), the gifts of the Holy Ghost are habitual dispositions of the soul, rendering it amenable to the motion of the Holy Ghost. Now the Holy Ghost moves us to this effect among others, of having a filial affection towards God, according to Romans 8:15, "You have received the spirit of adoption of sons, whereby we cry: Abba (Father)." And since it belongs properly to piety to pay duty and worship to one's father, it follows that piety, whereby, at the Holy Ghost's instigation, we pay worship and duty to God as our Father, is a gift of the Holy Ghost.
Reply to Objection 1. The piety that pays duty and worship to a father in the flesh is a virtue: but the piety that is a gift pays this to God as Father.
Reply to Objection 2. To pay worship to God as Creator, as religion does, is more excellent than to pay worship to one's father in the flesh, as the piety that is a virtue does. But to pay worship to God as Father is yet more excellent than to pay worship to God as Creator and Lord. Wherefore religion is greater than the virtue of piety: while the gift of piety is greater than religion.
Reply to Objection 3. As by the virtue of piety man pays duty and worship not only to his father in the flesh, but also to all his kindred on account of their being related to his father so by the gift of piety he pays worship and duty not only to God, but also to all men on account of their relationship to God. Hence it belongs to piety to honor the saints, and not to contradict the Scriptures whether one understands them or not, as Augustine says (De Doctr. Christ. ii). Consequently it also assists those who are in a state of unhappiness. And although this act has no place in heaven, especially after the Day of Judgment, yet piety will exercise its principal act, which is to revere God with filial affection: for it is then above all that this act will be fulfilled, according to Wisdom 5:5, "Behold how they are numbered among the children of God." The saints will also mutually honor one another. Now, however, before the Judgment Day, the saints have pity on those also who are living in this unhappy state.
Source: Summa Theologica (New Advent)