The reward of the servants is that they will have joy in the fruit of their labors. The Lord has said:
'And if it so be that you should labor all your days in crying repentance unto this people, and bring, save it be one soul unto me, how great shall be your joy with him in the kingdom of my Father!
And now, if your joy will be great with one soul that you have brought unto me into the kingdom of my Father, how great will be your joy if you should bring many souls unto me!' (DC 18:15-16).