Translation: It works the same with favorable things, if God out of plain generosity did not grant them to some of those asking, we might say He has nothing to do with them [good things]; likewise, if He gave them [the good things] to everybody asking for them, we might think them the owing to [superficial] devotion, and devotion of this kind would not make us godly but greedy and covetous.Similiter in rebus secundis, si non eas Deus quibusdam petentibus euidentissima largitate concederet, non ad eum ista pertinere diceremus; itemque si omnibus eas petentibus daret, non nisi propter talia praemia seruiendum illi esse arbitraremur, nec pios nos faceret talis seruitus, sed potius cupidos et auaros.
Problem: I can't make out the grammar of serviendum in relation to the clause non nisi propter talia praemia seruiendum illi esse arbitraremur.