Can I use my Schengen visa from a country that is different from the country it was issued from? I'm an Egyptian citizen who lives in Qatar but I want to travel from Egypt.
I dont think it will be a problem, Imagine if you are travelling to multiple countries, and take a visa for all three from your home country, you would naturally travel from a country other than the one which issued you a visa. Port of origin wont matter at all for any visa.
Specifically I am not able to find an evidence which can support my argument
Yes, you can.
The visa is your authorization to travel to the port of entry for the country that issued your the visa. It does not dictate from where you should travel. You can travel from Qatar, Egypt, or any other country.
I should mention though - some countries issue visas that dictate how you may travel. For example, Saudi Arabia can issue you a land or air visa. In this case, it only restricts how you enter the country - not necessarily where you leave.