This boon was granted by his father who was gratified-'You will not die without your own desire. Drona was born of the Brahmarshi Bharadvaja in a water pot.
पित्रा ह्युक्तः प्रसन्नेन नाकामस्त्वं मरिष्यसि। ब्रह्मर्षेच भरद्वाजाद् द्रोणो द्रोण्यामजायत॥