7. Allah Subhanahuthala taught a supplication to Adam (AS) and his wife along with other things before he sent to earth. What is that supplication?

السلام عليكم ورحمة الله وبركاتة    

ﺑِﺴْـــــــﻢِﷲِﺍﻟﺮَّﺣْﻤَﻦِﺍلرَّﺣِﻴﻢ

Answer:

قَالَا رَبَّنَا ظَلَمْنَآ أَنفُسَنَا وَإِن لَّمْ تَغْفِرْ لَنَا 

وَتَرْحَمْنَا لَنَكُونَنَّ مِنَ ٱلْخَـٰسِرِين

 "Our Lord, we have wronged ourselves, and if You do not forgive us and have mercy upon us, we will surely be among the losers." [7:23]

Explanation:

It is the first supplication mankind invokred to Allah Subhanahuthala.

Adam (AS) and his wife along with Shaithan were expelled from Paradise because they disobeyed the command of Allah.

Adam (AS) and his wife realized their mistake. Adam (AS) never blamed his wife and not even Shaithan for this mistake. They together repented with a supplication as mentioned in Quran as: "Adam received from his Lord [some] words" [2:37]. They invoked with those words whole heartedly. Allah accepted their repentance. He forgave them and made him a Prophet and from them the mankind was propagated.

Where as Shaithan never realised his disobediance and never repented for his mistake. Further he influenced  Adam (AS) and his wife, to disobey the Allah's command.  So he was cursed by Allah and remained as open enemy to mankind till the Day of Resurrection.

This dua is the best dua for mankind. Just like Adam (AS), his progeny was also greatly influenced by Shaithan. During such conditions, a man can say this dua of repentanc and forgiveness and get the Mercy of Allah. Allah Al Alim very well know the weaknesses and shortcomings of human beings and He is always Merciful!

الحمدلله