B.G 9.19

तपाम्यहमहं वर्षं निगृह्णाम्युत्सृजामि च। अमृतं चैव मृत्युश्च सदसच्चाहमर्जुन ॥१९॥

tapāmyahamahaṁ varṣaṁ nigr̥hṇāmyutsr̥jāmi ca। amr̥taṁ caiva mr̥tyuśca sadasaccāhamarjuna ॥19॥

[तपामि (tapāmi) - I heat; अहम् (aham) - I; अहं (aham) - I; वर्षं (varṣam) - rain; निगृह्णामि (nigṛhṇāmi) - withhold; उत्सृजामि (utsṛjāmi) - release; च (ca) - and; अमृतं (amṛtam) - immortality; च (ca) - and; एव (eva) - indeed; मृत्युḥ (mṛtyuḥ) - death; च (ca) - and; सद् (sat) - the effect; असत् (asat) - cause; च (ca) - and; अहम् (aham) - I; अर्जुन (arjuna) - O Arjuna;]

I am the source of heat, and I withhold and send forth the rain. O Arjuna, know that I encompass both immortality and death, and I am simultaneously the cause and effect.

Gīta Tātparya 9.19

Due to the completeness of virtuous qualities, supreme Lord Vishnu is called 'sat'. As no one else is superior in qualities to Lord Vishnu, i.e. He is beyond ordinary qualities. Hence he is spoken of as 'asat'.

"सत् साधुगुणपूर्णत्वादस्मान्नान्यो गुणाधिकः। यतोऽतोऽसदितिप्रोक्तं विष्ण्वाख्यं परमं पदम्॥"

"sat sādhuguṇapūrṇatvādasmānnānyo guṇādhikaḥ। yato'to'saditiproktaṁ viṣṇvākhyaṁ paramaṁ padam॥"

[सत् (sat) - truth, existence; साधुगुणपूर्णत्वात् (sādhuguṇapūrṇatvāt) - due to the completeness of virtuous qualities; अस्मान् (asmān) - us; नान्यो (nānyo) - no other; गुणाधिकः (guṇādhikaḥ) - superior in qualities; यत् (yat) - from which; अतोऽसत् (ato'sat) - from the non-existence; इति (iti) - thus; प्रोक्तं (proktaṃ) - is said; विष्ण्वाख्यं (viṣṇvākhyaṃ) - the name of Vishnu; परमं (paramam) - supreme; पदम् (padam) - state, position;]

"Due to the completeness of virtuous qualities, supreme Lord Vishnu is called 'sat'; no one else is superior in qualities to Lord Vishnu, i.e. He is beyond ordinary qualities, hence he is spoken as 'asat'."

इति शब्दनिर्णये ॥१६-१९॥

iti śabdanirṇaye ॥16-19॥

[इति (iti) - thus; शब्दनिर्णये (śabdanirṇaye) - in the determination of words;]

- stated thus in the śabdanirṇaya, a book on the determination of words.