Genesis - Chapter 15

This chapter begins "After this, the word of the LORD came to Abram in a vision."

And again, in verse 4, "Then the WORD of the LORD came to him".

This is the first time the phrase "word of the Lord" is used in the Bible, but it will be used many times after this.  This phrase definitely reminds us of Jesus - and at the beginning of John's gospel we read

In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God.

In the Old Testament there are several appearances of Jesus in person. These pre-incarnate appearances are known as theophanies.  The title used is usually "The angel of the LORD".  In those situations angel means a messenger, but not a created angel.  It is the second person of the Trinity.  Some commentators consider that this appearance of "The word of the LORD" is also a theophany - an appearance of Jesus himself to Abraham.