John 1:18

No human eye has ever seen God: the only Son, who is in the Father's bosom--He has made Him known.

John 12:41

Isaiah uttered these words because he saw His glory; and he spoke of Him.

Treasury of Scripture Knowledge

Summary

And when Gideon perceived that he was an angel of the LORD, Gideon said, Alas, O Lord GOD! for because I have seen an angel of the LORD face to face.

Bible References

Because

John 1:18
No human eye has ever seen God: the only Son, who is in the Father's bosom--He has made Him known.
John 12:41
Isaiah uttered these words because he saw His glory; and he spoke of Him.