When Moses twisted his head.

During the restoration of Michelangelo's Moses, completed in 2002, many unexpected findings were made, including significant modifications in the final years between 1542-45. The theory is supported by a great scholar on Michelangelo: Christoph L. Frommel.  In his biography on the artist Michelangelo una vita inquieta (2005) chief restorer Antonio Forcellino describes how the artist worked over time.  
According to a document recently discovered by Forcellino, Michelangelo would have turned the head of Moses 25 years after his first version.  A letter from an anonymous acquaintance of the artist reports (shortly after Michelangelo's death) how the master had turned the head of Moses at a later time. Frommel noticed how oddly enough art history makes no reference to the fact.
Other elements discovered during the restoration seem to confirm the theory:
- the massive beard pulled to the right, presumably because on the left there was not enough marble left after the torsion;
- the throne of Moses is lowered on the left and to place the left foot back the artist is forced to tighten the knee;
- for the first time since the days of Canova the rear part of the statue was examined: a belt survives (which disappeared from the front).
Apparently the reason who prompted Michelangelo to turn Moses' head was religious.
Moses does not turn around and grab his beard to 'tame his passion' and save the tablets as Sigmund Freud had suggested. 
According to Frommel Moses looks away from the altar where the venerated chains of Peter granted indulgences to countless pilgrims. 
Just as if he had seen a new golden calf.
Further evidence for Michelangelo's involvement with Reformation circles.