This sermon is going to nail the debate on who built Petra to Rest. Let us begin with the name of Petra, the real name.
And in the thirtieth jubilee, [1429 A.M.] in the second week, in the first year thereof, he took to himself a wife, and her name was Melka, the daughter of Madai, the son of Japheth, and in the fourth year [1432 A.M.] he begat a son, and called his name Shelah; for he said: 'Truly I have been sent.'
[And in the fourth year he was born], and Shelah grew up and took to himself a wife, and her name was Mu'ak, the daughter of Kesed, his father's brother, in the one and thirtieth jubilee, in the fifth week, in the first year [1499 A.M.] thereof.
Shelah is the name of the son Kainam who is the son of Arpachshad, who is the son of Shem. We do find this name in the Bible
16 Send ye the lamb to the ruler of the land from Sela to the wilderness, unto the mount of the daughter of Zion.
Sela-H5554-סֶלַעÇelaʻ, seh'-lah; the same as H5553; Sela, the rock-city of Idumaea:—rock, Sela(-h).
Edom (Greek, Idumaea), an ancient country in , south of Palestine , between the Dead Sea and the Gulf of Aqaba ; named for the Edomites. In the second half of the second millennium B.C., the land was settled by the Edomites, who united to form a state in the late second millennium B.C.
It is very important to understand that the Edomites came to Petra and Resettled the area.
Who is Edom?
אֱדֹםʼĔdôm, ed-ome'; or (fully) אֱדוֹם H123-Edom:ʼĔdôwm ; from H122; red (see Genesis 25:25); Edom, the elder twin-brother of Jacob; hence the region (Idumaea) occupied by him:—Edom, Edomites, Idumea
Where is the Valley Of Moses?
Wadi Musa (Arabic: وادي موسى, literally "Valley of Moses") is a town located in the Ma'an Governorate in southern Jordan. It is the administrative center of the Petra Department and the nearest town to the archaeological site of Petra.
Knowing that Shelah took a wife had children and build his own city we can safely say that Petra is named after him.
I will sing of the mercies of the Lord for ever: with my mouth will I make known thy faithfulness to all generations.
2 For I have said, Mercy shall be built up for ever: thy faithfulness shalt thou establish in the very heavens.
3 I have made a covenant with my chosen, I have sworn unto David my servant,
4 Thy seed will I establish forever, and build up thy throne to all generations. Selah.
The Name Selah means: Truley I have been sent.
If you take the time from when Shelah had his son, in 1499 and subtract from the current Hebrew Year of 5782 we learn that it was about 4283 years ago Petra was built.