Bhagavad Gita: Chapter 9, Verse 16-17

अहं क्रतुरहं यज्ञ: स्वधाहमहमौषधम् |
मन्त्रोऽहमहमेवाज्यमहमग्निरहं हुतम् || 16||
पिताहमस्य जगतो माता धाता पितामह: |
वेद्यं पवित्रमोङ्कार ऋक्साम यजुरेव च || 17||

ahaṁ kratur ahaṁ yajñaḥ svadhāham aham auṣhadham
mantro ’ham aham evājyam aham agnir ahaṁ hutam
pitāham asya jagato mātā dhātā pitāmahaḥ
vedyaṁ pavitram oṁkāra ṛik sāma yajur eva cha

aham—I; kratuḥ—Vedic ritual; aham—I; yajñaḥ—sacrifice; svadhā—oblation; aham—I; aham—I; auṣhadham—medicinal herb; mantraḥ—Vedic mantra; aham—I; aham—I; eva—also; ājyam—clarified butter; aham—I; agniḥ—fire; aham—I; hutam—the act offering; pitā—father; aham—I; asya—of this; jagataḥ—universe; mātā—mother; dhātā—sustainer; pitāmahaḥ—grandsire; vedyam—the goal of knowledge; pavitram—the purifier; om-kāra—the sacred syllable Om; ṛik—the Rig Veda; sāma—the Sama Veda; yajuḥ—the Yajur Veda; eva—also; cha—and

aham kratur aham yajnah svadhaham aham aushadham
mantro ’ham aham evajyam aham agnir aham hutam
pitaham asya jagato mata dhata pitamahah
vedyam pavitram omkara rik sama yajur eva cha

Translation

BG 9.16-17: It is I who am the Vedic ritual, I am the sacrifice, and I am the oblation offered to the ancestors. I am the medicinal herb, and I am the Vedic mantra. I am the clarified butter, I am the fire and the act of offering. Of this universe, I am the Father; I am also the Mother, the Sustainer, and the Grandsire. I am the purifier, the goal of knowledge, the sacred syllable Om. I am the Ṛig Veda, Sāma Veda, and the Yajur Veda.

Commentary

In these verses, Shree Krishna gives a glimpse into the various aspects of His infinite personality.  Kratu means yajña (sacrifice), such as agnihotra yajñas mentioned in the Vedas.  It also refers to the yajñas, such as vaiśhva deva that are described in the Smṛiti scriptures.  Auṣhadham refers to the potency in medicinal herbs.

Creation emanates from God, and hence He is its Pitā (Father).  Before creation, He holds the unmanifested material energy in His womb, and so He is also its Mātā (Mother).  He maintains the universe and nourishes it, and thus He is its Dhātā (Sustainer).  He is also the Father of Brahma, who is the creator, and hence, He is the Grandfather of this universe.

The Vedas have emanated from God.  The Ramayan states:  jākī sahaja svāsa śhruti chārī  “God manifested the Vedas by His breath.”  They are the knowledge potency of God, and hence an aspect of His unlimited personality.  Shree Krishna states this truth dramatically by saying that He is the Vedas.