Note:
I couldn't decide between these two quotes for Thanksgiving here
in the United States, so today you get 2 instead of 1.
In
prosperity, give thanks to God with humility and fear lest by pride
you abuse God's benefits and so offend him.
–-
Saint Louis IX from a letter to his son
Dear
friends, now that we have received instruction in this revelation of
God's grace, let us celebrate with spiritual joy the day of our first
harvesting, of the first calling of the Gentiles. Let us give thanks
to the merciful God, "who has made us worthy," in the words
of the Apostle, "to share the position of the saints in light;
who has rescued us from the power of darkness, and brought us into
the kingdom of this beloved Son."
–-
Pope Saint Leo the Great from a sermon