Bhagavad Gita · 10.32

सर्गाणामादिरन्तश्च मध्यं चैवाहमर्जुन।अध्यात्मविद्या विद्यानां वादः प्रवदतामहम्॥

sargāṇām ādir antaśh cha madhyaṁ chaivāham arjuna adhyātma-vidyā vidyānāṁ vādaḥ pravadatām aham

Of all creations, I am the beginning, the end, and also the middle, O Arjuna. Among sciences, I am the science of the self (adhyatma-vidya). Among debaters, I am logical reasoning.

— Bhagavad Gita 10.32

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)