The features of rajo-guṇa is very active, but for sense gratification. Just like ordinary persons, they are very active. They rise also early in the morning, they work very hard, but the whole plan is for sense gratification. That's all. That is rajo-guṇa. And sattva-guṇa means they are silent, they are sober, they know what is what, and they try for spiritual advancement. That is sattva-guṇa.
So you can understand whether a man is in sattva-guṇa or a man is in rajo-guṇa or a man is in tamo-guṇa by the symptoms of his behavior. So as we associate with different types of guṇas we develop a certain type of mentality that continues, and if it continues up to the point of death, then certainly we'll have to accept a body influenced by these guṇas.
Therefore Bhagavad-gītā says, prakṛteḥ kriyamāṇāni guṇaiḥ karmāṇi sarvaśaḥ (BG 3.27). Yasmāt, these guṇaiḥ. Prakṛteḥ kriyamāṇāni guṇaiḥ. According to the association of guṇa, or quality, prakṛti gives you a certain type of body. The body is given by prakṛti, by nature. Therefore, nature is called mother, Durgā.
Just like we develop this body exactly from the mother's womb. The father gives the seed, but the bodily ingredients, that is . . . just like mother is developing her body, similarly, she is developing the child's body also, by eating, by the secretion, by development of the secretion, air. Air is solidifying the secretion. It is becoming gradually muscles, skin, bone, as it is becoming harder and harder. A very nice factory is going on. That is also by nature. And nature is working by the order of Kṛṣṇa. Therefore, ultimate cause is Kṛṣṇa.