Albert Barnes Commentary Deuteronomy 3:11

"(For only Og king of Bashan remained of the remnant of the Rephaim; behold, his bedstead was a bedstead of iron; is it not in Rabbah of the children of Ammon? nine cubits was the length thereof, and four cubits the breadth of it, after the cubit of a man.)" — Deuteronomy 3:11 (ASV)

Giants - Or Rephaim: see the marginal reference note.

A bedstead of iron - The “iron” was probably the black basalt of the country, which not only contains a large proportion (about 20 percent) of iron, but was actually called “iron,” and is still so regarded by the Arabians. Iron was indeed known and used at the time in question by the Semitic people of Palestine and the adjoining countries, principally for tools (see, for example, Deuteronomy 19:5 and compare Genesis 4:22 note); but bronze was the ordinary metal of which weapons, articles of furniture, etc., were made.

The word translated “bedstead” is derived from a root meaning “to unite” or “bind together,” and thus “to arch” or “cover with a vault.” The word may then certainly mean “bier,” and perhaps does so in this passage. Modern travelers have discovered in the territories of Og sarcophagi as well as many other articles made of the black basalt of the country.

Is it not in Rabbath of the children of Ammon? - Probably, after the defeat and death of Og at Edrei, the remnant of his army fled into the territory of the friendly Ammonites, and carried with them the corpse of the giant king.

After the cubit of a man - That is, according to the usual and ordinary cubit, measured by the common human standard. Taking 18 inches to the cubit, the bedstead or sarcophagus would thus be from thirteen to fourteen feet long.