3.17

यस्त्वात्मरतिरेव स्यादात्मतृप्तश्च मानवः ।
आत्मन्येव च सन्तुष्टस्तस्य कार्यं न विद्यते ॥

yas tv ātmaratir eva syād ātmatṛptaś ca mānavaḥ
ātmany eva ca santuṣṭas tasya kāryaṃ na vidyate

śrībhagavān (श्रीभगवान्) is speaking, and tu (तु) marks the exception to the wheel.

The verse

But the person who delights only in the self, is content in the self, and is satisfied in the self alone — for him nothing remains that must be done.

नेपालीमा

तर जो केवल आत्मामा रमाउँछ, आत्मामा तृप्त छ, र केवल आत्मामा सन्तुष्ट छ, त्यसका लागि गर्नुपर्ने केही बाँकी रहँदैन।

Where it sits

This is the person 3.4 was protecting when it refused cheap renunciation: he is real, and for him the wheel is not a duty. 3.18 will say he has nothing to gain by acting or by not acting, and 3.19 turns back to everyone else.

Split: यः + तु + आत्म-रतिः + एव + स्यात् + आत्म-तृप्तः + च + मानवः + आत्मनि + एव + च + सन्तुष्टः + तस्य + कार्यम् + न + विद्यते

yaḥ + tu + ātma-ratiḥ + eva + syāt + ātma-tṛptaḥ + ca + mānavaḥ + ātmani + eva + ca + santuṣṭaḥ + tasya + kāryam + na + vidyate

Sanskrit, in depth

The words

देवनागरीWordGrammarSense
यःyaḥnominativewho.
तुtuindeclinablebut.
आत्म-रतिःātma-ratiḥnominativehe whose delight is in the self.
एवevaindeclinablealone, only.
स्यात्syātoptative, 3rd singular of as (अस्)he should be, if he be.
आत्म-तृप्तःātma-tṛptaḥnominativecontent in the self.
चcaindeclinableand.
मानवःmānavaḥnominativea human being.
आत्मनिātmanilocativein the self.
एवevaindeclinablealone.
चcaindeclinableand.
सन्तुष्टःsantuṣṭaḥnominativesatisfied.
तस्यtasyagenitivefor him, of him.
कार्यम्kāryamnominativea thing that must be done.
नnaindeclinablenot.
विद्यतेvidyatepresent, 3rd singularthere is, it is found.

The phrases

यस् तु आत्मरतिः एव स्यात् yas tv ātmaratir eva syāt is the first of three conditions. But the person who delights only in the self. रतिः + एव ratiḥ + eva is ratir eva (रतिरेव). iḥ (इः) before a vowel becomes ir (इर्).

आत्मतृप्तः च मानवः ātmatṛptaś ca mānavaḥ is the second. And content in the self. तृप्तः + च tṛptaḥ + ca is tṛptaś ca (तृप्तश्च), aḥ (अः) before c (च्) becoming ś (श्). syāt (स्यात्) before ātma (आत्म) has voiced: syād ātma (स्यादात्म).

आत्मनि एव च सन्तुष्टः तस्य कार्यम् न विद्यते ātmani eva ca santuṣṭas tasya kāryaṃ na vidyate is the third, and the consequence. And satisfied in the self alone — for him there is nothing that has to be done. सन्तुष्टः + तस्य santuṣṭaḥ + tasya is santuṣṭas tasya (सन्तुष्टस्तस्य).

Sanskrit in this line

iḥ (इः) before a vowel becomes ir (इर्), as uḥ (उः) became ur (उर्) in 3.16. ātma-ratiḥ eva (आत्मरतिः एव) is recited ātmaratir eva (आत्मरतिरेव). The delight-word and the "only" are one sound. Do not leave a visarga between them.

Say it back

Three phrases with ātman (आत्मन्), then the consequence. If you can say the consequence of 3.16 and not this one, you have missed the tu (तु).