Yahweh (the Christ) visited Abraham by the Oaks

I replied again, “If I could not have proved to you from the Scriptures that one of those three is God, and is called Angel, because, as I already said, He brings messages to those to whom God the Maker of all things wishes [messages to be brought], then in regard to Him who appeared to Abraham on earth in human form in like manner as the two angels who came with Him, and who was God even before the creation of the world, it were reasonable for you to entertain the same belief as is entertained by the whole of your nation.”

“… And now have you not perceived, my friends, that one of the three, who is both God and Lord, and ministers to Him who is in the heavens, is Lord of the two angels?”

Justin Martyr
Dialogue with Typho
Chapter LVI

When you say that this Christ existed as God before the ages..

And Trypho said, “We have heard what you think of these matters. Resume the discourse where you left off, and bring it to an end. For some of it appears to me to be paradoxical, and wholly incapable of proof. For when you say that this Christ existed as God before the ages, then that He submitted to be born and become man, yet that He is not man of man, this [assertion] appears to me to be not merely paradoxical, but also foolish.”

Justin Martyr
Dialogue with Trypho
Chapter XLVIII

Gentiles should not be forced to follow Jewish law

And Trypho again inquired, “But if some one, knowing that this is so, after he recognizes that this man is Christ, and has believed in and obeys Him, wishes, however, to observe these [institutions], will he be saved?” I said, “In my opinion, Trypho, such an one will be saved, if he does not strive in every way to persuade other men, —I mean those Gentiles who have been circumcised from error by Christ, to observe the same things as himself, telling them that they will not be saved unless they do so. This you did yourself at the commencement of the discourse, when you declared that I would not be saved unless I observe these institutions.”

Justin Martyr
Dialogue with Trypho
Chapter XLVII

Mary is the the end of the Old Covenant

“As, then, circumcision began with Abraham, and the Sabbath and sacrifices and offerings and feasts with Moses, and it has been proved they were enjoined on account of the hardness of your people’s heart, so it was necessary, in accordance with the Father’s will, that they should have an end in Him who was born of a virgin, of the family of Abraham and tribe of Judah, and of David…”

Justin Martyr
Dialogue with Trypho
Chapter XLIII

Eucharistic sacrifice prophesied in the Old Testament

“And the offering of fine flour, sirs,” I said, “which was prescribed to be presented on behalf of those purified from leprosy, was a type of the bread of the Eucharist, the celebration of which our Lord Jesus Christ prescribed, in remembrance of the suffering which He endured on behalf of those who are purified in soul from all iniquity, in order that we may at the same time thank God for having created the world, with all things therein, for the sake of man, and for delivering us from the evil in which we were, and for utterly overthrowing principalities and powers by Him who suffered according to His will. Hence God speaks by the mouth of Malachi, one of the twelve [prophets], as I said before, about the sacrifices at that time presented by you: ‘I have no pleasure in you, saith the Lord; and I will not accept your sacrifices at your hands: for, from the rising of the sun unto the going down of the same, My name has been glorified among the Gentiles, and in every place incense is offered to My name, and a pure offering: for My name is great among the Gentiles, saith the Lord: but ye profane it.” [So] He then speaks of those Gentiles, namely us, who in every place offer sacrifices to Him, i.e.,the bread of the Eucharist, and also the cup of the Eucharist, affirming both that we glorify His name, and that you profane [it].

Justin Martyr
Dialogue with Trypho
Chapter XLI