The following are some of the many laws relating to the Shemonah-esreh,
or the eighteen blessings which form the most devotional part of daily
worship, and which are repeated three times on (ordinary) week-days, and
four times on Sabbaths, new moons, and on appointed feasts:--

Before commencing the Shemonah-esreh one should step back three paces,
in order to be able to advance three steps. The reason of this is that
Moses our Rabbi--peace be on him!--advanced before his prayer into the
three divisions, "darkness, clouds, and thick darkness" (Deut. iv. 11).
And this is also the reason why after finishing the Shemonah-esreh three
steps backward are to be made, returning through these three parts or
divisions.

This prayer is to be performed standing, and the feet so joined together
that they should seem as it were one foot only, in order to be like the
angels, of whom it is written (Ezek. i. 7), "And their feet were (so in
the original) a straight foot," that is to say, their feet appeared as
one foot.

This attitude is a sign that the power of locomotion is gone; he cannot
pursue and attain any other object than God. The Gentiles place their
hands together, intending to signify thereby that their hands are as it
were bound; but we, by placing our feet together, intend to signify that
they are as it were entirely bound, which is indicative of greater
humility; for with the hands bound one could still run away in search of
his own pleasure, which he cannot do when the feet are bound.

THE KABBALA, _Kitzur Sh'lh_, fol. 48, col. 2, and fol. 49, col. 1.