The Sages state that Jewish schoolchildren were diligently engaged in Torah study and prayer, while fasting, throughout the three days that preceded Esther’s entry to the king. Their cries reached the heavenly Throne and ultimately abrogated Haman’s wicked decree.

After Haman made the gallows, he went to Mordekhai and found him sitting in the study hall, and children were sitting before him, with sackcloth on their loins, and they were engaged in Torah study, and screaming and crying. Haman counted them and found that there were twenty-two thousand children there. He threw iron chains over them, and appointed guards over them, saying: Tomorrow I will kill these children first, and then I will hang Mordekhai.

Their mothers brought them bread and water, and said to them: Our children, eat and drink before you die tomorrow, so you will not die hungry.

Immediately the children placed their hands upon their books and took oaths on Mordekhai’s life: Our Master, we will neither eat nor drink, but rather we will die while in the midst of our fast. They all burst into tears until their cries rose to the heavens, and the Holy One, blessed be He, heard the sound of their cries in the second hour of the night.

At that hour the mercies of the Holy One, blessed be He, were awakened, and He arose from upon the Throne of judgment and said: What is this great noise that I hear, which is like the bleating of goats and lambs? Moses our Master stood before the Holy One, blessed be He, and said: Master of the Universe, they are neither goats nor lambs, but rather they are the young of Your people who have been fasting for three days and three nights, and tomorrow the enemy wants to slaughter them like goats and lambs. At that moment, the Holy One, blessed be He, took hold of those letters that he decreed on them, which were sealed with a seal of mud, and He tore them. He caused Ahashverosh to become confused that night, and that is the meaning of what is written: “On that night, the king’s sleep was disrupted” (Esther 6:1). (Esther Rabba 9)