SB 6.16.57

yad etad vismṛtaṁ puṁso
 mad-bhāvaṁ bhinnam ātmanaḥ
tataḥ saṁsāra etasya
 dehād deho mṛter mṛtiḥ
Word for word: 
yat — which; etat — this; vismṛtam — forgotten; puṁsaḥ — of the living entity; mat-bhāvam — My spiritual position; bhinnam — separation; ātmanaḥ — from the Supreme Soul; tataḥ — from that; saṁsāraḥ — material, conditional life; etasya — of the living entity; dehāt — from one body; dehaḥ — another body; mṛteḥ — from one death; mṛtiḥ — another death.
Translation: 
When a living entity, thinking himself different from Me, forgets his spiritual identity of qualitative oneness with Me in eternity, knowledge and bliss, his material, conditional life begins. In other words, instead of identifying his interest with Mine, he becomes interested in his bodily expansions like his wife, children and material possessions. In this way, by the influence of his actions, one body comes from another, and after one death, another death takes place.
Purport: 

Generally the Māyāvādī philosophers or persons influenced by Māyāvādī philosophers think themselves as good as the Supreme Personality of Godhead. This is the cause of their conditional life. As stated by the Vaiṣṇava poet Jagadānanda Paṇḍita in his Prema-vivarta:

kṛṣṇa-bahirmukha hañā bhoga vāñchā kare
 nikaṭa-stha māyā tāre jāpaṭiyā dhare

As soon as a living entity forgets his constitutional position and endeavors to become one with the Supreme, his conditional life begins. The conception that the Supreme Brahman and the living entity are equal not only in quality but also in quantity is the cause of conditional life. If one forgets the difference between the Supreme Lord and the living entity, his conditional life begins. Conditional life means giving up one body to accept another and undergoing death to accept death again. The Māyāvādī philosopher teaches the philosophy of tat tvam asi, saying, “You are the same as God.” He forgets that tat tvam asi applies in terms of the marginal position of the living entity, who is like sunshine. There is heat and light in the sun, and there is heat and light in the sunshine, and thus they are qualitatively one. But one should not forget that the sunshine rests on the sun. As the Lord says in Bhagavad-gītā, brahmaṇo hi pratiṣṭhāham: “I am the original source of Brahman.” The sunshine is important because of the presence of the sun globe. It is not that the sun globe is important because of the all-pervasiveness of the sunshine. Forgetfulness and misunderstanding of this fact is called māyā. Because of forgetfulness of one’s constitutional position and that of the Supreme Lord, one comes into māyā, or saṁsāra — conditional life. In this regard, Madhvācārya says:

sarva-bhinnaṁ parātmānaṁ
 vismaran saṁsared iha
abhinnaṁ saṁsmaran yāti
 tamo nāsty atra saṁśayaḥ

When one thinks that the living entity is nondifferent in all respects from the Supreme Lord, there is no doubt that he is in ignorance (tamaḥ).