Sheik Ilderim pins a Star of David onto Ben Hur's belt before the race, obviously to goad the Romans. The Star of David didn't become a symbol of Judaism until the Middle Ages, in Eastern Europe. The first reference occurs in the 12th Century.
The mezuzah shown at the entrance to Ben-Hur's home is mounted diagonally. That practice was not adopted until the middle ages, by Ashkenazi Jews, as a compromise between the rules offered by 2 medieval Rabbis.
When Judah and Messala argue in the courtyard of Judah's home, road noise and honking horns from cars can be heard in the background. For some reason, it was not removed from the soundtrack in post prodction.
In the market scene following the argument between Messala and Judah, a person is heard saying in the background 'kidhar jaata hai bhai, kidhar jaata hai' which is hindi for 'where are you going brother, where?'.
Hindi language originated much later in the 17-18th century.
As the Romans are marching to Jerusalem, Drusus asks Messala what town they are passing through. Messala replies, "Nazareth," but when he says "we arrive in Jerusalem tomorrow night," his mouth is not moving.
In the film's prologue, Balthasar the narrator states that Jesus's takes place "in the seventh year of the reign of Augustus Caesar." In fact Augustus had been emperor of Rome for at least 20 years at the time.
Sheikh Ilderim and Judah pronounce the name of the Sheikh's chariot horse "REEGH-el," as though it were from the Latin, with a hard "g." The four horses, as the Sheikh, are "named for the stars," and all those names -- Aldebaran, Altair, Antares and Rigel -- are Arabic names for these particularly bright stars that are still in use. An Arab would pronounce that last name as "Rijl" (REE-djl), not "REEGH-el," and Judah would likely have known that.
When Messala assumes command of the garrison, outgoing commander Sextus is seen in the doorway as they are going into the barracks, yet when Messala speaks to Drusus about finally taking command, in the closeup shot Sextus is not in the doorway.
In the overhead view of the second turn as the chariots are taking their parade lap around the race course heading toward the starting line, there should have been hoof and wheel tracks from when the chariots made their entry onto the race course. All we see are the tracks of the horses leading the parade.
Jesus' ministry seems to last 5 years in this movie. Although this is traditionally seen as lasting only 3 years, the Bible gives no such specific chronology, Making it 5 years is a reasonable artistic decision.
A character refers to the Roman Emperor as "The Divine Tiberius." Although Tiberius was never deified in life (it was a posthumous honour), he claimed descent from the Roman deities Jupiter and Venus, so he was "divine" in that sense. Tiberius' successor Caligula claimed in his madness to be all gods at once, and Caligula's successor Claudius I was the first of the office to be formally deified during his lifetime.
It is well documented that Messala's horses in the chariot race were dyed black (their natural color was brown). They appear solid black during the pre-race procedures. During the race, when the horses are running flat out, most of the dye wore off and in closeups, they appear to be brown.
During the chariot race just before Ben-Hur's chariot jumps the wrecked chariot, stunt driver Joe Canutt can be seen dropping the reins and grabbing hold of the side of the his chariot (his father, stunt coordinator-2nd unit director Yakima Canutt, had instructed him to grip the underside of the chariot's railing. Joe ignored him, or forgot, and grasped the railing from the top, and was vaulted over the top of the chariot, which could have been fatal had his quick reflexes and strength not allowed him to haul himself back over the vehicle's yoke before he fell between the horses and chariot).
When Esther and Tirzah and Miriam seek shelter, the storm is violent enough to cause earth to fall in front of the cave, and the sound of the wind is deafening. Yet trees visible in the background (from the mouth of the cave) do not so much as sway in the breeze.
When Christ is carrying His cross, the Latin title Iesus Nazarenus, Rex Iudaeorum ("Jesus of Nazareth, the King of the Jews") is written backwards. A Roman soldier is shown carrying the title ahead of Him, with the Latin characters reversed (from right to left). A few moments later the title appears again, only this time the Latin is written correctly (from left to right).
Christ is always seen from the back, but when He is condemned to death He is facing Pilate and His face is obscured by a shadow added optically in post production when William Wyler determined that actor Claude Heater's face was too clearly seen, even at a distance.
The goof items below may give away important plot points.
Nine chariots start the chariot race. After the first crash, there appear still to be nine chariots in the race. After the third crash, six are shown, but as Ben Hur passes to catch up, clearly there is a total of seven in the race. After five have crashed, five are left. Messala is the sixth chariot to crash, but Ben Hur and three others finish the race. Thus, nine chariots start the race, six crash, and four finish.