E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Enter a House right Foot fore most (Petronius).
It was thought unlucky to enter a house or to leave ones chamber left foot foremost. Augustus was very superstitious on this point. Pythagoras taught that it is necessary to put the shoe on the right foot first. When stretching forth your feet to have your sandals put on, first extend your right foot (Protreptics of Iamblichus, symbol xii.). Iamblichus tells us this symbolised that mans first duty is reverence to the gods.