Śāstra means you can consult. Just like you consult dictionary, you consult encyclopedia, you consult so many authoritative books for understanding knowledge, similarly, if you consult, you get all information. So in this Śrīmad-Bhāgavatam it is all stated: "If you do like this, you get birth like this. If you do like this, you get birth like this."
And in the Śrīmad Bhagavad-gītā it is generally spoken, ūrdhvaṁ gacchanti sattva-sthāḥ (BG 14.18). Those who are in the modes of goodness . . . there are three qualities in this material world: the quality of goodness, the quality of passion and the quality of ignorance. So in the Bhagavad-gītā it is stated that ūrdhvaṁ gacchanti sattva-sthāḥ: those who are cultivating the quality of goodness, they can be promoted to the higher status of life in higher planetary system. Ūrdhvam. Ūrdhvam means higher. Ūrdhvaṁ gacchanti sattva-sthāḥ.
And madhye tiṣṭhanti rājasāḥ. Rājasāḥ means those who are in the modes of passion. They remain either in this planet or some of them may be elevated to the heavenly planet. Heavenly planet is also in the middle of the universe. And adho gacchanti tāmasāḥ jaghanya-guṇa-vṛtti-sthāḥ. Jaghanya—very abominable characters. Jaghanya-guṇa-vṛtti-sthāḥ. Those who are situated not only ignorance . . . out of ignorance, one remains in abominable condition. So jaghanya-guṇa-vṛtti-sthā adho gacchanti tāmasāḥ (BG 14.18): they go downwards, even to the animal life. So we have to consult and we have to mold our life in that way.