You had sworn that you would protect (all persons in the enjoyment of their own). This oath of yours was not rigidly kept by you. You took also what belonged to a Brahmana. This has been the twofold sin, you have perpetrated.
रक्षितास्मीति चोक्तं ते प्रतिज्ञा चानृता तव। ब्राह्मणस्वस्य चादानं द्विविधस्ते व्यतिक्रमः॥