सत्त्वं रजस्तम इति गुणाः प्रकृतिसंभवाः।
निबध्नन्ति महाबाहो देहे देहिनमव्ययम्।।14.5।।
14.5 O mighty-armed one, the alities, viz sattva, rajas and tamas, born of Nature, being the immutable embodies being to the body.
14.5 The three Gunas of Prakrti - Sattva, Rajas and Tamas - are inherent in the essential nature of Prakrti and are particular expressions of it. They can be known only through their effects such as brightness etc. They are not apparent in the unevolved state of Prakrti but become apparent in its transformations as Mahat etc. They bind the self, which is conjoined with bodies such as those of divinities, men etc., composed of the modifications of Prakrti beginning with Mahat and ending with the elements. The self is immutable, i.e., It is not in Its pristine nature conjoined with the Gunas. But the Gunas bind It when residing in the body. The meaning is that they bind It by virtue of the limiting conditions of Its living in the body. Sri Krsna proceeds to speak of the nature of Sattva, Rajas and Tamas and their modes of binding (the self):
Sattwam rajastama iti gunaah prakriti sambhavaah; Nibadhnanti mahaabaaho dehe dehinam avyayam.
sattvam—mode of goodness; rajaḥ—mode of passion; tamaḥ—mode of ignorance; iti—thus; guṇāḥ—modes; prakṛiti—material nature; sambhavāḥ—consists of; nibadhnanti—bind; mahā-bāho—mighty-armed one; dehe—in the body; dehinam—the embodied soul; avyayam—eternal