First man with a set of religious texts is resolute (7)
I believe the answer is:
adamant
'resolute' is the definition.
(both can mean determined)
'first man with a set of religious texts' is the wordplay.
'first' is a charade indicator (letters next to each other).
'man' becomes 'adam' (Adam is an example).
'with' says to put letters next to each other.
'set of religious texts' becomes 'NT' (New Testament).
'adam'+'a'='adama'
'adama' put next to 'nt' is 'ADAMANT'.
'is' is the link.
(Other definitions for adamant that I've seen before include "Unshakable (in an opinion)" , "Hard stone" , "Refusing to budge" , "Inflexible, obdurate" , "Legendary rock" .)