As long as Moses held his hands up…(Ex. 17:11)

Moses' raising his hands [in the battle against Amalek] was a matter of his concentrating on his ten fingers being pointed at what is called "the heights of the Heavens". The central column of the [structure of the] sefirot is known as "heights", with the vowel shuruk.

Whenever Moses' concentration flagged, the accusing finger of the celestial representative of Amalek made itself felt….

Moses did something similar to what the priests do when they raise their hands in the priestly blessing. By concentrating on the number ten they also concentrate on the ten sefirot and the source of blessing that flows from that region to disembodied spirits. At such a time the power of any force opposing such prayers is checked and its influence halted (at least temporarily). At such moments the Israelite soldiers would be victorious.

The words "…Israel was stronger"(ibid.) was therefore something closely linked to Moses' continued ability or willingness to raise his fingers and concentrate on the number ten. Whenever Moses' concentration flagged, the accusing finger of the celestial representative of Amalek made itself felt and the Israelites retreated.

It is forbidden to stand with outstretched hands in prayer for more than three hours….

Moses was compelled to lower his hands from time to time as it is not admissible to interfere with opposing spiritual forces to such an extent that one neutralizes them altogether. G‑d has not created forces in the universe in order for them to be totally ineffective. This is what the prophet Isaiah also had in mind when he said of G‑d creating the earth: "He did not create it a waste, but formed it for habitation." (Isaiah 45:18) This statement includes all the phenomena G‑d has created, not just those that we appreciate or are fond of.

Consider the matter as if in order to have balance in the world the forces of evil have a role assigned to them and it is not up to any man to totally deny them unless the premise for their existence has been removed - i.e. unless all people are good all the time. The Midrash expresses this by saying that it is forbidden to stand with outstretched hands in prayer for more than three hours.

[Selected with permission from the seven-volume English edition of "The Torah Commentary of Rebbeinu Bachya" by Eliyahu Munk.]