Theory:

     Next day, early in the morning, when the sprightly sunrays embellished themselves for their journey down to earth, the sun said, “It’s our day off again. We’re staying up here. The road to earth is blocked by an army of thick, mucky clouds.” The little rays so much wanted to go down for a lark but they remained quiet. One of them, though, who had made a pact with little Saeeda said, “Sir, I can’t stay back. I’ve given my word to Saeeda whose mother is ill and needs our help. I’ll pierce through the clouds to reach Saeeda’s courtyard. How else will her mother be cured?” Hearing this, all the rays nearly staged a revolt against their father, the sun. “Fancy staying back again,” they said in a single voice. “What will the people of the earth say about us? That we of the heavens have turned liars?”
 
     The sun relented. “Please yourselves,” he said. “Mind your clothes, though. The clouds are mucky.”
Explanation:
 
The next day arrived, and the sunrays were all set to go down to the earth. But then their father, the sun, appeared before them. He told them that they are not expected to be on the earth on that particular day.
 
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Sun stopped the rays from going to the earth
 
Since the rainy clouds have an earth duty and have occupied the skies like the previous days, the sun and his rays will stay in their home.
 
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Mucky clouds were blocking the sun's path to the earth
 
The little rays were disappointed. They had wanted to go down to the earth very badly. Especially, given that they didn't have much of the earth time during the previous days. The journey to the earth is more like a picnic or an adventure to them. Although they weren't happy about the day's off duty, they decided to remain quiet and sit at home.
 
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The rays were disappointed
 
However, the little ray who had made a promise to Saeeda couldn't remain quiet. She told her father (the sun) that she has to travel down to the earth. She told him about the promise she had made, and about how Saeeda's mother requires their help. The little ray was determined to keep her promise, and hence said that she would reach Saeeda’s courtyard by piercing through the clouds.
 
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The little ray said that she would pierce through the clouds
 
When the little ray had voiced out her decision, the rest of the rays joined her in the protest. They reminded the sun that they would be seen as liars by the humans if the sun and his rays do not keep their word.
 
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The rays protested against their father
 
Finally, the sun changed his mind and yielded to their request. However, he warned the little rays by saying that the path down to the earth is blocked by clouds that are quite dirty. Hence, they should take care of themselves.
 
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The sun finally agreed but warned them not to get dirty
  
Meanings of difficult words:
  
No.
Word
Meanings
1
Sprightly Full of energy
2
Embellished Dressed up
3
Day offHoliday
4
An army of clouds Group of clouds; the word "army" is used to make the situation seem more dangerous and war-like.
5
Mucky Covered with dirt
6
LarkAn activity done for enjoyment or amusement
7
PactA formal agreement between two people or groups of people
8
RelentTo become less severe towards a situation
9
RevoltAn attempt to take a violent action against an authority
Reference:
National Council of Educational Research and Training (2006). A Pact With The Sun. (pp. 28-32). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.