Question

My question is, relating to the above phrase, why is the dative 'seinem' used. This is part of an exercise written in German using a dash , which indicates that a particular ending should be used. Seinem is supposed to be the correct answer and I can't see why this should be.

Answer 1

I read and read and it made no sense to me the presence of a dative. Then I wound up finding a text with what seems to be the original sentence you've mistyped.

Instead of "Freunde", the text contains "Freude", word that goes along the lines of joy, happiness, but also, due to context and good phrasing, to favor, pleasing (noun), maybe "sake". So "eine Freude machen" could roughly translate to "do a favor (to)" -  and here comes the dative conception, following this "to".

As a matter of fact, the page whereon I've found the text translates this segment to:
"The Caliph, who had always rather favoured the Grand Vizier" http://www.german-grammar.de/exercises/table_of_content/tales/kalif_storch/seite02/seite_02.htm