Targum sobre Exodo 26:28

And the middle bar in the midst of the boards passing from end to end shall be from the tree which Abraham planted in Beara of Sheba: for when Israel had crossed the sea, the angels cut down the tree and cast it into the sea, and it floated on the face of the waters. And an angel proclaimed, and said, This is the tree which Abraham planted in Beara of Sheba, and prayed there in the name of the Word of the Lord. And the sons of Israel shall take and make thereof the middle bar, seventy cubits in length, and with it shall wondrous things be done: for when they have reared up the tabernacle, it shall go round it like a serpent among the boards of the tabernacle and when they take it down, it shall become straight as a rod.