Why are there so many languages when the origin is one?
Question

                Why are there so many languages in the world when we know that all nations are one in origin, namely our father Adam and our mother Hawwa’?
Praise be to Allah.
      Allah knows best. Your Lord is the Most Wise, All-Knowing. We do not have 
      any certain knowledge of the wisdom behind that, but we know that our Lord 
      is Most Wise, All-Knowing. He, may He be glorified and exalted, says 
      (interpretation of the meaning):

    “Certainly your Lord is Most Wise, All-Knowing”

    [al-An ‘aam 6:83]

    “And Allah is Ever All-Knowing, Most Wise”

    [an-Nisa’ 4:11]. 
By 
    His great wisdom, He made many languages and made people of different 
    colours, as He, may He be glorified and exalted, says (interpretation of the 
    meaning):

    “And among 
    His Signs is the creation of the heavens and the earth, and the difference 
    of your languages and colours”

    [ar-Room 30:22]. 

    The reason may be so as to highlight His almighty power, for He, may He be 
    glorified, is able to make one language for some people and another language 
    for others, for this is more indicative of great power. 

    There may be other reasons for it of which we are unaware and that we cannot 
    comprehend, but scholars other than us may understand them. 

    The point is that one of the clearest reasons behind it is that He, may He 
    be glorified and exalted, is able to do all things, therefore He gave people 
    many languages and told us that this is one of His signs (interpretation of 
    the meaning): “And 
    among His Signs is the creation of the heavens and the earth, and the 
    difference of your languages and colours” 
    [ar-Room 30:22]. 

    Just as He made them of many colours, including red, black and white, and 
    shades in between, and He has caused them to vary in size, so that some are 
    tall and some are short, and some are in between, and He has caused you to 
    vary in attitude and intellect, the same also applies to the issue of 
    languages. All of that is indicative of His almighty power and highlights 
    the fact that He does whatever He wills, may He be glorified and exalted, 
    and there may be other great reasons behind that which we do not understand. 
    End quote. 

    Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him).