Abu Amr al-Shaybani (may Allah have mercy on him) said: I came to Sayyiduna Ibn Mas'ud (may Allah be pleased with him) with some runaway slaves from Yemen, and he said: "There is reward in this and also spoils." I said: As for the reward, we know it; what are the spoils? He said: "Forty dirhams for every person."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9034