Bg 4.6

ajo ’pi sann avyayātmā
bhūtānām īśvaro ’pi san
prakṛtiṁ svām adhiṣṭhāya
sambhavāmy ātma-māyayā

Word for word: 

ajaḥ — unborn; api — although; san — being so; avyaya — without deterioration; ātmā — body; bhūtānām — of all those who are born; īśvaraḥ — the Supreme Lord; api — although; san — being so; prakṛtim — in the transcendental form; svām — of Myself; adhiṣṭhāya — being so situated; sambhavāmi — I do incarnate; ātma–māyayā — by My internal energy.

Translation: 

Although I am unborn and My transcendental body never deteriorates, and although I am the Lord of all living entities, I still appear in every millennium in My original transcendental form.

 

BG 4.6

Very important and technical verse, Vaishnava Acharyas and Mayavadis has practically fought war on this verse. The debate was whether Supreme Lord is taking material form or maintains His own form. When Krishna is saying my Prakriti it means Prakriti is under His control and adjusting it I MANIFEST.

I MANIFEST Myself by internal potency.

Srila Prabhupad says Prakriti means His nature as well as His Swarupa. He doesn’t change His nature, By His mercy He appears in this material world, He appears for the sake of all living entities.

He comes by his own arrangement for the benefit of everyone, so when He appears He doesn’t come under control of His material nature rather material nature always remains under His control. Srila Prabhupad gives example of a prisoner (Jiva) going to jail and a prime minister (Bhagvan) visiting jail.

Lord’s incarnation is a great mystery, sometimes people are not able to understand His spiritual form. Materialistic people think his form as material and like him. Example – Shishupal, Duryodhna thought like that