What is the ruling behind using the letter Sa'd when there is a little 'seen' on top of it?

Question
What is the ruling behind using the letter Sa'd when there is a little 'seen' on top of it?

Answer
Assalaam alaikum,
There are some Arabic words that originally have a , but when the letter  is near it, it is pronounced and written by some Arabs tribes as a .  This is reflected in the Qur'an, as it was revealed in the language of the Arabs.  There are four words in the Qur'an in which the is written with a and read by some of the Qira'aat or in some of the turuq of Hafs with a and by other turuq or other qira'aat as a .  Sometimes in one tareeq or qira'ah it is allowed to read it either with a or a
These four words are the words in red in the following examples:




In the Medina Printing Complex copy of the Qur'an for Hafs, the words are written with the reading of Hafs 'an 'Aasim by the tareeq Ash-Shaatibiyyah in mind.  The first two examples are read with a , and thesmall letter is written above the to show that we read it with a .  In the third example, it is allowed to read with either the  or the , so the is written below the .  In the last example, it is read with only a by Hafs 'an 'Aasim by the tareeq of Ash-Shatibiyyah, so it is written with the only, with no small  added in the enhancements of the writing. 
We cannot use the placement of the over or under the as a tool in other musaahif as they may not be following the qira'ah of Hafs or not the tareeq of Ash-Shaatibiyyah. 
If you are only reading Hafs 'an 'Aasim by the tareeq of Ash-Shatibiyyah, then you should follow the rules outlined for reading with a or a in the four words above irregardless as to the placement of the small over or under the in the copy of the Qur'an that you are using.