The Mongols have sent a traitor into the Japanese camp. If they can't be defeated by the horde, can they be defeated by an enemy within?
then you shouldn't sell 
your services for free.
فلا ينبغي إذاً أن تقدّم خدماتك بالمجّان
solltest du deine Dienste
nicht für lau feilbieten.
no ofrezcas tus servicios gratuitamente.
no ofrezcas tus servicios gratuitamente.
n’offre pas gratuitement
tes services.
non dovresti offrire i tuoi servizi gratuitamente.
você não deveria oferecer 
os seus serviços de graça.
то не продашь свои навыки за спасибо.