Mahabharata 13.101.47

यस्मादूर्ध्वगमेतत्तु तमसश्चैव भेषजम्तस्मादूर्ध्वगतेर्दाता भवेदिति विनिश्चयः

yasmādūrdhvagametattu tamasaścaiva bheṣajamtasmādūrdhvagaterdātā bhavediti viniścayaḥ

Our plain-language meaning of this verse is waiting for scholar review.