He was the author of the famous rule which bears his name; it was praised by St. Benedict and is still observed by the monks of the East. The Holy Ghost filled him with His divine wisdom and with intelligence (Introit): when, therefore, he wrote against those who rebelled against the sound doctrine (Epistle), he attacked the Arians, who denied the divinity of Jesus Christ and prepared the triumph of orthodoxy over the error of the Macedonians by firmly establishing the Catholic dogma regarding the Holy Ghost.
He is one of the four great Doctors of the East. He died in 379.
Let us ask St. Basil to fill us with his faith in the divinity of the third Person of the Holy Trinity, and to deliver us from sin (Offertory) which hinders the working of the Holy Ghost in our souls.
In medio Ecclesiae aperuit os ejus: et implevit eum Dominus spiritu sapientiae et intellectus: stolam gloriae induit eum. * Bonum est confiteri Domino: et psallere nomini tuo, Altissime.
In the midst of the Church the Lord opened his mouth: and He filled him with the spirit of wisdom and understanding: He clothed him with a robe of glory. * It is good to give praise to the Lord: and to sing to Thy name, O most High.
(Ecclesiasticus 15:5 and Psalm 91:2 from the Introit of Mass)
Exaudi, quaesumus, Domine, preces nostras, quas in beati Basilii Confessoris tui atque Pontificis solemnitate deferimus: et, qui tibi digne meruit famulari, ejus intercedentibus meritis, ab omnibus nos absolve peccatis.
Graciously hear, we beseech Thee, O Lord, the prayers we offer to Thee on this festival day of blessed Basil, Thy confessor and bishop : he deserved to render Thee a worthy service ; may his merits appeal to Thee to absolve us from all our sins. Through our Lord.
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/02330b.htm