Wherefore the Offertory declares that he had been chosen by Jesus to be one of the twelve princes who would govern His Church: "the Lord has crowned him with glory and honour and has given him authority over the works of His hands."
"The Lord," the Epistle also says, "has given him his share of inheritance among the twelve tribes." The country of the Parthians and Persians was allotted to St Thomas when the Apostles divided the world among themselves. Let us prepare for tomorrow's solemnity in union with the Holy Church.
Ego autem sicut oliva fructifera in domo Domini, speravi in misericordia Dei mei: et exspectabo nomen tuum, quoniam bonum est ante conspectum sanctorum tuorum. * Quid gloriaris in malitia: qui potens es in iniquitate?
But I, as a fruitful olive-tree in the house of the Lord, have hoped in the mercy of my God: and I will wait on Thy name, for it is good in the sight of Thy saints. * Why dost thou glory in malice, thou that art mighty in iniquity?
(Psalm 51:10-11,3 from the Introit of Mass)
Grant, we beseech Thee, almighty God, that the solemn feast of Thine Apostle Thomas, which we anticipate, may both increase our devotion and advance our salvation.
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/14658b.htm