Is the Son part of the triune God?
Yes, the Son is part of the triune God. The context explicitly states that the Son is a part of the triune God, and that by Him God created the world. This affirms the Son's deity and role in creation.
Les explains that Hebrews 1 presents the Son as part of the triune God. The passage says God has spoken in these last days by His Son, whom He appointed heir of all things, and by whom He also made the world. Les uses this to show that Christ was a creator, affirming His place within the triune Godhead. He also notes that the ascended Lord revealed the book of Revelation to John, further demonstrating the Son's divine role.
Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;