Bg 10.8

aham sarvasya prabhavo
mattah sarvam pravartate
iti matva bhajante mam
budha bhava-samanvitah

Word for word: 
aham — I; sarvasya — of all; prabhavah — the source of generation; mattah — from Me; sarvam — everything; pravartate — emanates; iti — thus; matva — knowing; bhajante — become devoted; mam — unto Me; budhah — the learned; bhava-samanvitah — with great attention.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
I am the source of all spiritual and material worlds. Everything emanates from Me. The wise who perfectly know this engage in My devotional service and worship Me with all their hearts.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
A learned scholar who has studied the Vedas perfectly and has information from authorities like Lord Caitanya and who knows how to apply these teachings can understand that Krishna is the origin of everything in both the material and spiritual worlds, and because he knows this perfectly he becomes firmly fixed in the devotional service of the Supreme Lord. He can never be deviated by any amount of nonsensical commentaries or by fools. All Vedic literature agrees that Krishna is the source of Brahma, Siva and all other demigods. In the Atharva Veda (Gopala-tapani Upanisad 1.24) it is said, yo brahmanam vidadhati purvam yo vai vedams ca gapayati sma Krishnah: “It was Krishna who in the beginning instructed Brahma in Vedic knowledge and who disseminated Vedic knowledge in the past.” Then again the Narayana Upanisad (1) says, atha puruso ha vai narayano ’kamayata prajah srjeyeti: “Then the Supreme Personality Narayana desired to create living entities.” The Upanisad continues, narayanad brahma jayate, narayanad prajapatih prajayate, narayanad indro jayate, narayanad astau vasavo jayante, narayanad ekadasa rudra jayante, narayanad dvadasadityah: “From Narayana, Brahma is born, and from Narayana the patriarchs are also born. From Narayana, Indra is born, from Narayana the eight Vasus are born, from Narayana the eleven Rudras are born, from Narayana the twelve Adityas are born.” This Narayana is an expansion of Krishna.

It is said in the same Vedas, brahmanyo devaki-putrah: “The son of Devaki, Krishna, is the Supreme Personality.” (Narayana Upanisad 4) Then it is said, eko vai narayana asin na brahma nesano napo nagni-somau neme dyav-aprthivi na naksatrani na suryah: “In the beginning of the creation there was only the Supreme Personality Narayana. There was no Brahma, no Siva, no water, no fire, no moon, no heaven and earth, no stars in the sky, no sun.” (Maha Upanisad 1.2) In the Maha Upanisad it is also said that Lord Siva was born from the forehead of the Supreme Lord. Thus the Vedas say that it is the Supreme Lord, the creator of Brahma and Siva, who is to be worshiped.

In the Moksa-dharma section of the Mahabharata, Krishna also says,

prajapatim ca rudram capy
aham eva srjami vai
tau hi mam na vijanito
mama maya-vimohitau

“The patriarchs, Siva and others are created by Me, though they do not know that they are created by Me because they are deluded by My illusory energy.” In the Varaha Purana it is also said,

narayanah paro devas
tasmaj jatas caturmukhah
tasmad rudro ’bhavad devah
sa ca sarva-jnatam gatah

“Narayana is the Supreme Personality of Godhead, and from Him Brahma was born, from whom Siva was born.”

Lord Krishna is the source of all generations, and He is called the most efficient cause of everything. He says, “Because everything is born of Me, I am the original source of all. Everything is under Me; no one is above Me.” There is no supreme controller other than Krishna. One who understands Krishna in such a way from a bona fide spiritual master, with references from Vedic literature, engages all his energy in Krishna consciousness and becomes a truly learned man. In comparison to him, all others, who do not know Krishna properly, are but fools. Only a fool would consider Krishna to be an ordinary man. A Krishna conscious person should not be bewildered by fools; he should avoid all unauthorized commentaries and interpretations on Bhagavad-gita and proceed in Krishna consciousness with determination and firmness.