Genesis 31:13

I am Eloha who did reveal Myself to thee at Beth El where thou didst anoint the pillar, and swear the oath before Me. Arise now, go forth from this land, and return to the land of thy birth.

I AM THE G-D OF BETH-EL. Jacob related to his wives all that G-d’s angel had told him in the dream, all this serving to persuade them to go with him. However, what he told did not consist of one dream. The statement, Lift up now thine eyes, and see, all the he-goats was made to him when he served Laban for his flock, at the time the flock conceived in one of the first years. The statement, I am the G-d of Beth-el was made to him after that, at the time of the journey, for after He said to him, Now arise, get thee out from this land, he no longer remained in Haran to further tend Laban’s flocks so that the he-goats would mount the flocks and the flocks would give birth to speckled and spotted. But on the morrow of the dream, he sent for Rachel and Leah and told them his dream, and they left Haran.
I am ‘ha’e-il’ (the G-d) of Beth-el. The meaning thereof is, as Rashi explained it, that the letter hei in ha’e-il is redundant and is the same as if it were written: “I am e-il Beth-el (the G-d of Beth-el).” Similarly, To ‘ha’aretz’ (the land) of Canaan; [the hei is redundant and is the same as if it were written: “to eretz Canaan (the land of Canaan).”] Grammarians adjusted it by saying that it is as if it were written, “I am the G-d, who is the G-d of Beth-el.” Similarly, And the tree of the knowledge of good and evil, [which is as if it said: “and the tree of the knowledge, namely the knowledge of good and evil”]; the cords of gold, [which is as if it said, “the cords, which are cords of gold]. And the angel here speaks in the name of He Who sent him, [therefore, he speaks in the first person and says, “I am, etc.”] ….

WHERE THOU DIDST ANOINT A PILLAR, WHERE THOU DIDST VOW A VOW UNTO ME. The meaning thereof is that “you have vowed to worship the Proper Name of the Eternal in the Chosen Land, and that this stone should be to you a house of G-d in which to set aside your tithes, and if you further delay the fulfillment of your vows, G-d might yet be angry at your voice.”

אשר משחת, in order to sanctify it; so far you have not offered a sacrifice on it that would discharge your vow.

אנכי הא-ל בית א-ל, the noun to which the word בית א-ל is attached is absent, i.e. the line should have been:אנכי הא-ל א-ל בית א-ל. We have a similar construction in Joshua 3,14 הארון הברית, where the word ארון in the middle in the construct mode is also missing. In our verse the meaning of the whole line is: “I am the Lord that has revealed Himself to you as G’d at Beyt El.”

אשר נדרת לי, we already explained that when the angel speaks as messenger of G’d he describes himself by the name applicable to his Master, i.e. to G’d.