57 Keep, I pray You, this my pious faith undefiled, and even till my spirit departs, grant that this may be the utterance of my convictions: so that I may ever hold fast that which I professed in the creed of my regeneration, when I was baptized in the Father, and the Son, and the Holy Spirit. Let me, in short, adore You our Father, and Your Son together with You; let me win the favour of Your Holy Spirit, Who is from You, through Your Only-begotten. For I have a convincing Witness to my faith, Who says, Father, all Mine are Yours, and Yours are Mine, even my Lord Jesus Christ, abiding in You, and from You, and with You, for ever God: Who is blessed for ever and ever. Amen.
Source: On the Trinity (New Advent)