The Council of Ephesus (431 AD)

If any man shall say that the one Lord Jesus Christ was glorified by the Holy Ghost, so that he used through him a power not his own and from him received power against unclean spirits and power to work miracles before men and shall not rather confess that it was his own Spirit through which he worked these divine signs; let him be anathema.

If anyone says that the form of a servant is of like nature with the Holy Ghost, and not rather that it owes its union with the Word which has existed since the conception, to his mediation, by which it works miraculous healings among men, and possesses the power of expelling demons; let him be anathema.

The scope of this anathematism is to shew that the Word of God, when he assumed flesh remaining what he was, and lacking nothing which the Father possessed except only paternity, had as his own the Holy Spirit which is from him and substantially abides in him. From this it follows that through him, as through a power and strength which was his own, and not one alien or adventitious, he wrought his wonders and cast forth devils, but he did not receive that Holy Spirit and his power as formerly the Prophets had done, or as afterwards his disciples did, as a kind of gift (beneficii loco).

The Orientals objected that St. Cyril here contradicts himself, for here he says that Christ did not work his wonders by the Holy Ghost and in another place he frankly confesses that he did so work them. But the whole point is what is intended by working through the Holy Ghost. For the Apostles worked miracles through the Holy Ghost but as by a power external to themselves, but not so Christ. When Christ worked wonders through the Holy Ghost, he was working through a power which was his own, viz.: the Third Person of the Holy Trinity; from whom he never was and never could be separated, ever abiding with him and the Eternal Father in the Divine Unity.

The Westerns have always pointed to this anathematism as shewing that St. Cyril recognized the eternal relation of the Holy Spirit as being from the Son.