AC 5663.

[2]  That the Lord was meant in the Word by "God" and "Jehovah" the Jewish Church did not know, nor does the Christian Church know it at this day. That the Christian Church has not known it is because it has distinguished the Divinity into three persons. But the Ancient Church which was after the flood, and above all the Most Ancient Church which was before the flood, understood by "Jehovah" and "God" no other than the Lord, and Him indeed as to His Divine Human. They also knew about the Divine Itself which is in the Lord, and which He calls His "Father" yet they were not able to think about that Divine Itself which is in the Lord, but about the Divine Human, and consequently could not be conjoined with any other Divine; for conjunction is effected through thought which is of the understanding and affection which is of the will, thus through faith and through love. For if we think of the Divine Itself, the thought falls as it were into a boundless universe, and thus is dissipated, whence there is no conjunction. It is otherwise when the Divine Itself is thought of as the Divine Human. And the ancients knew that they could not be saved unless they were conjoined with the Divine.

[3] Therefore it was the Divine Human that the Ancient Churches worshiped; and Jehovah also manifested Himself to them in the Divine Human. The Divine Human was the Divine Itself in heaven; for heaven constitutes one man, which is called the Grand Man, as has been heretofore shown at the end of the chapters. This Divine in heaven is none other than the Divine Itself, but in heaven it is as a Divine Man. This Man is what the Lord took on and made Divine in Him, and united it to the Divine Itself as it had been united from eternity; for from eternity there was a one. He did this because mankind could not otherwise have been saved; for it was no longer sufficient for the Divine Itself to be able, through heaven and thus through the Divine Human Itself there, to flow into human minds; wherefore the Divine Itself willed to unite the Divine Human to Itself actually by the Human taken on in the world. The one and the other is the Lord.