After the seventh plague that God visited upon Egypt – the plague of hail – Pharaoh summoned Moshe and confessed his guilt, whereupon Moshe promised to bring an end to the plague. He told the king that he would leave the city and then outstretch his hands to the Almighty in prayer, begging Him to end the destructive storm: “Moshe said to him, ‘When I leave the city, I will spread my hands out to the Lord…’” (Shemot 9:29). Indeed, the Torah tells several verses later (9:33), “Moshe left from Pharaoh’s presence [and left] the city, and he spread his hands out to the Lord…”
The practice to spread one’s hands out during prayer is mentioned in other contexts, as well. In Sefer Melakhim I (8:54), we read that King Shlomo’s hands were spread when he recited his famous prayer at the time of the dedication of the Beit Ha-mikdash. After Avraham’s successful battle to rescue Sedom, he told the city’s king, “I lift my hand to the Supreme God” (Bereishit 14:22), which Onkelos translates as a reference to prayer (“I lift my hand in prayer before the Lord”). And the Midrash (Bereishit Rabba 60:14) describes Yitzchak as standing with “his hand outstretched in prayer” when Rivka saw him for the first time.
Rav Yissachar Ber Eilenburg, in his Be’er Sheva (responsum 71), raises the question of why this practice is not customarily observed. Although it is clear from the aforementioned sources that a number of righteous Biblical figures prayed with their arms outstretched, this practice is not mentioned in halakhic literature and is not commonly observed.
Rav Eilenburg suggests that this practice perhaps stopped being followed once it became common among followers of other faiths. He notes Chazal’s comment (cited by Rashi, Devarim 16:22) that the patriarchs erected monuments as religious symbols, but the Torah forbids doing so because this had become a widespread custom among pagans. Possibly, then, this is also why the custom of spreading one’s hands during prayer is also not commonly observed among Jews.
Rav Yaakov Emden, in the introduction to his Beit Yaakov commentary to the siddur, suggests a different theory based on the aforementioned comment in the Midrash regarding Rivka’s initial encounter with Yitzchak. Rivka saw Yitzchak with his hands outstretched in prayer, the Midrash relates, and she then recognized that he was a uniquely righteous individual. Rav Yaakov Emden thus concludes that this was a practice observed only by the exceedingly righteous, and it is possible that later generations felt unworthy of praying in this fashion.
Along somewhat similar lines, Rav Chaim Binyamin Pontremoli, in his Petach Ha-devir commentary to the Orach Chayim section of the Shulchan Arukh (89), suggests that outstretching one’s hands during prayer means avowing that one’s “hands” are pure and innocent of impropriety. The hands represent one’s professional activity, and one who outstretches his hand to God is proclaiming that he is innocent of any sort of wrongdoing, such as theft or dishonesty, in his work. If one prays in this fashion but is not truly innocent of impropriety, then he is called to task for his false avowal of innocence, and for this reason, Rav Pontremoli suggests, people stopped observing this practice, as they did not feel confident enough to proclaim their total innocence of impropriety in their jobs and their commercial pursuits.
(Based on Rav Asher Anshel Schwartz, Ma’adanei Asher, Parashat Vaera, 5777)