SB 11.11.2

śoka-mohau sukhaṁ duḥkhaṁ
 dehāpattiś ca māyayā
svapno yathātmanaḥ khyātiḥ
 saṁsṛtir na tu vāstavī
Synonyms: 
śoka — lamentation; mohau — and illusion; sukham — happiness; duḥkham — distress; deha-āpattiḥ — accepting a material body; ca — also; māyayā — by the influence of māyā; svapnaḥ — a dream; yathā — just as; ātmanaḥ — of the intelligence; khyātiḥ — merely an idea; saṁsṛtiḥ — material existence; na — is not; tu — indeed; vāstavī — real.
Translation: 
Just as a dream is merely a creation of one’s intelligence but has no actual substance, similarly, material lamentation, illusion, happiness, distress and the acceptance of the material body under the influence of māyā are all creations of My illusory energy. In other words, material existence has no essential reality.
Purport: 

The word deha-āpattiḥ indicates that the living entity falsely identifies himself with the external material body and thus transmigrates from one body to another. Āpatti also indicates great suffering or misfortune. Because of such false identification under the influence of illusion, the living entity experiences the miserable symptoms described here. Māyā means the false concept that anything can exist without Lord Kṛṣṇa or for any purpose other than the pleasure of the Supreme Lord. Although the conditioned living entities are trying to enjoy material sense gratification, the result is always painful, and such painful experiences turn the conditioned soul back toward the Supreme Personality of Godhead. In other words, the ultimate purpose of the material creation is to bring the living entity back to the loving devotional service of the Lord. Therefore, even the sufferings of the material world may be seen as the transcendental mercy of the Personality of Godhead. The conditioned soul, imagining that material objects are meant for his personal enjoyment, bitterly laments the loss of such objects. In this verse, the example is given of a dream in which the material intelligence creates many illusory objects. Similarly, our polluted material consciousness creates the false impression of material sense gratification, but this phantasmagoria, being devoid of Kṛṣṇa consciousness, has no real existence. By surrendering to polluted material consciousness, the living entity is afflicted with innumerable troubles. The only solution is to see Lord Kṛṣṇa within everything and everything within Lord Kṛṣṇa. Thus, one understands that Lord Kṛṣṇa is the supreme enjoyer, the proprietor of everything and the well-wishing friend of all living beings.

In material illusion there is no understanding of one’s eternal, spiritual body, nor is there knowledge of the Absolute Truth. Therefore, material existence, even in its most sophisticated or pious form, is always foolishness. One should not misunderstand the example of the dream to mean that the material world has no real existence. Material nature is the manifestation of the Lord’s external potency, just as the spiritual sky is the manifestation of the Lord’s internal potency. Although material objects are subject to transformation and thus have no permanent existence, the material energy is real because it comes from the supreme reality, Lord Kṛṣṇa. It is only our false acceptance of the material body as the factual self and our foolish dream that the material world is meant for our pleasure that have no real existence. They are merely mental concoctions. One should cleanse oneself of material designations and wake up to the all-pervading reality of the Personality of Godhead, Lord Kṛṣṇa.