1 Gita Sloka Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 5

The entire content of this mail is from Swami Adidevananda's translation of Ramanuja's  Gita  Bhashya and Swami Chidbhavananda's Bhagavad Gita, both published by Ramakrishna Mission

The next stanza clarifies further

The Function of the Gunas 5-10

1 Gita Sloka  Every Day - Chapter 14 - Gunatraya Vibhaga Yoga - Sloka 5

Sattvam rajah tama iti gunah prakriti sambhavah I

Nibhandhanti mahabaho dehe dehinam  avyayam II sloka 5

सत्त्व रजः तम इति गुणः प्रकृति संभवः I 
निभन्धन्ति महाबाहो देहे देहिनम् अव्ययम्  II श्लोक 5

Sattva, Rajas and Tamas - these gunas, O mighty armed one, born of prakriti, bind the indestructible embodied one fast in the body.

The prakriti is made of three gunas.They are inherent in the essential nature of prakriti and are particular expressions of it. They can be known only by their effects such as 'brightness' etc. They are not apparent in the unevolved state of prakriti but become apparent in its transformation as Mahat, etc. They bind the self, which is conjoined with bodies such as those of divinities, men etc. composed of the modifications of prakriti beginning with mahat and ending with the elements.  The self is immutable ie. it is not in its pristine nature conjoined with the gunas. But 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 Krishna then begins to speak of the nature of the Sattva, Rajas and Tamas and the modes of binding.