The Trinity in the Old Testament

As a Christian I believe that God has been a Trinity (Father, Son, and Holy Spirit, three-in-one) since eternity past, which means that He was a Trinity in the time of the Old Testament as well as in the New Testament. There are many examples of this fact and many volumes written on the topic. Micah and I are in the process of reading through the Bible together, and a few days ago we ran across a chapter in Judges with a fairly obvious example of God manifested as a Trinity that neither of us had ever noticed before. In Judges 13 the Angel of Yahweh (translated LORD in all-caps in most English Bibles) comes to Manoah and his wife to announce that the woman's barren womb will be opened and that she will give birth to Samson. After the couple speaks with the Angel of Yahweh he ascends into heaven in the flame of a burnt offering that they present to Yahweh. Here is the passage that follows that event (Judges 13:21-25, ESV):

21The angel of the LORD appeared no more to Manoah and to his wife. Then Manoah knew that he was the angel of the LORD. 22And Manoah said to his wife, "We shall surely die, for we have seen God." 23But his wife said to him, "If the LORD had meant to kill us, he would not have accepted a burnt offering and a grain offering at our hands, or shown us all these things, or now announced to us such things as these." 24And the woman bore a son and called his name Samson. And the young man grew, and the LORD blessed him. 25And the Spirit of the LORD began to stir him in Mahaneh-dan, between Zorah and Eshtaol.

In case you didn't catch it (like I didn't all the times when I read this before), here's how the Trinity is present:
1. I believe Manoah when he says that he and his wife "have seen God." They have seen a person that is God Himself manifest before humans in an earthly setting. This is Jesus Christ. In fact, most--and arguably all--of the appearances of someone called "the Angel of Yahweh" in the Old Testament are appearances of Jesus. Again, there are volumes written on this subject.
2. Clearly God the Father is also present. He sends the Angel of Yahweh, he accepts the burnt offering and grain offering as Yahweh, He exercises providence over the lives of Manoah and his wife to bring about the birth of Samson, and He blesses Samson.
3. The Spirit of Yahweh in v. 25 is (obviously) God the Holy Spirit, who comes to stir the heart of Samson.

This is nothing new or groundbreaking, but I found it too good not to share. Now go and worship the triune God of the Bible.