When we discuss Saint Thomas Aquinas we often think of him as a philosopher (the five arguments for the existence of God) or as a theologian (transubstantiation). However, he was also a biblical scholar who wrote a number of commentaries.
Thomas wrote five Old Testament commentaries (that I know of). He wrote a commentary of the book of Job; a commentary on the Psalms (albeit only Psalms 1 through 51). He also wrote a commentary on the Canticle of Canticles. He also wrote a commentary on Isaiah and another on Jeremiah.
As for the New Testament, Thomas composed what was later called the Catena Aurea, which is Latin for "Golden Chain". This is a collection of saying of the Church Fathers for each verse of the four Gospels.
He also wrote a commentary on all the epistles of Saint Paul, in which Thomas included the epistle to the Hebrews as Pauline. Thomas attributes the more ornate style of Hebrews to Saint Luke and describes the epistle sicut a Paulo editae (as edited by Paul). Furthermore, Thomas explains that Paul left off his name because he was odious to the Jews of Palestine and was merely the Apostle to the Gentiles.
If you have a chance, check out Thomas Aquinas' commentaries, especially his commentary on Hebrews.
Here's an English translation: