Srimad Bhagavatam Canto 08, Chapter 04, Text 15

SB 8.4.15

yathanukirtayanty etac
 chreyas-kama dvijatayah
sucayah pratar utthaya
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Therefore, after getting up from bed in the morning, those who desire their own welfare — especially the brahmanas, ksatriyas, vaisyas and in particular the brahmana Vaisnavas — should chant this narration as it is, without deviation, to counteract the troubles of bad dreams.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Every verse in the Vedic literature, especially in the Srimad-Bhagavatam and Bhagavad-gita, is a Vedic mantra. Here the words yathanukirtayanti are used to recommend that this literature be presented as it is. Unscrupulous persons, however, deviate from the actual narration and interpret the text in their own way with grammatical jugglery. Such deviations are to be avoided. This is a Vedic injunction supported by Sukadeva Gosvami, one of the mahajanas, or authorities. He says, yathanukirtayanti: one should recite the mantra as it is, without deviation, for then one will be eligible to rise to the platform of all good fortune. Sukadeva Gosvami especially recommends that those who are brahmanas (sucayah) recite all these mantras after rising from bed in the morning.
Because of sinful activities, at night we have bad dreams, which are very troublesome. Indeed, Maharaja Yudhisthira was obliged to see hell because of a slight deviation from devotional service to the Lord. Therefore, duhsvapna — bad dreams — occur because of sinful activities. A devotee sometimes accepts a sinful person as his disciple, and to counteract the sinful reactions he accepts from the disciple, he has to see a bad dream. Nonetheless, the spiritual master is so kind that in spite of having bad dreams due to the sinful disciple, he accepts this troublesome business for the deliverance of the victims of Kali-yuga. After initiation, therefore, a disciple should be extremely careful not to commit again any sinful act that might cause difficulties for himself and the spiritual master. Before the Deity, before the fire, before the spiritual master and before the Vaisnavas, the honest disciple promises to refrain from all sinful activity. Therefore he must not again commit sinful acts and thus create a troublesome situation.
Srimad Bhagavatam Canto 08, Chapter 04, Text 14
Srimad Bhagavatam Canto 08, Chapter 04, Text 16