In Genesis 18, the Lord is mentioned several times. Along with 2 angels, he meets with Abraham. Is the Bible speaking of Jesus?
It does not explicitly state such, but it is possible to logically deduce it.
Technically, however, Avraham wouldn't have seen Yeshu'a of Nazareth, the incarnate Word of God. Rather, he would have seen the pre-incarnate Word. (Of course, I'd say most Christians don't find it necessary to make such a distinction.)
Many early Church fathers believed that Avraham and the other patriarchs saw God the Son when they are said to have seen God.
In Dialogue with Trypho, Ch. LVI §1, Justin Martyr wrote,
Two persons, both God, one who is sent (the Son), and the other who sends (the Father).