30 You have now had evidence of God the Judge as Lord and Lord; learn next that there is the same joint ownership of name in the case of God and God. Jacob, when he fled through fear of his brother, saw in his dream a ladder resting upon the earth and reaching to heaven, and the angels of God ascending and descending upon it, and the Lord resting above it, Who gave him all the blessings which He had bestowed upon Abraham and Isaac. At a later time God spoke to him thus: And God said unto Jacob, Arise, go up to the place Bethel, and dwell there, and make there an altar unto God, that appeared unto you when you fled from the face of your brother. God demands honour for God, and makes it clear that demand is on behalf of Another than Himself. He who appeared to you when you fled are His words: He guards carefully against any confusion of the Persons. It is God Who speaks, and God of Whom He speaks. Their majesty is asserted by the combination of Both under Their true Name of God, while the words plainly declare Their several existence.
Source: On the Trinity (New Advent)