Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 17
Sanskrit:
अमोघवीर्यो राजर्षिर्महिष्यां वीर्यमादधे ।श्वोभूते स्वपुरं यात: कालेनासूत सा सुतम् ॥ १७ ॥
ITRANS:
amogha-vīryo rājarṣirmahiṣyāṁ vīryam ādadheśvo-bhūte sva-puraṁ yātaḥkālenāsūta sā sutam
Translation:
King Duṣmanta, who never discharged semen without a result, placed his semen at night in the womb of his Queen, Śakuntalā, and in the morning he returned to his palace. Thereafter, in due course of time, Śakuntalā gave birth to a son.