if you want to divide a list of names in google sheets

If you want to group only the first fifth:

=TEXTJOIN(", ", TRUE,$A$2:INDEX($A$2:$A,ROUNDUP(COUNTA(A2:A)/5)))

or if you want group all:

=TEXTJOIN(", ", TRUE,FILTER($A:$A,ROW($A:$A)>=(ROUNDUP(COUNTA($A:$A)/5)*(ROW()-2)+2),ROW($A:$A)<=(ROUNDUP(COUNTA($A:$A)/5)*(ROW()-1)+1)))