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 Bhāshya 9.19

In the current context 'Sat' means the effect, and 'Asat' is used to mean the cause. Same is substantiated through testimonials.

"सत् कार्यम्। असत् कारनम्। सदभिव्यक्तरुपत्वात् कारणं चापि शब्दितम्॥"

"sat kāryam। asat kāranam। sadabhivyaktarupatvāt kāraṇaṁ cāpi śabditam॥"

[सत् (sat) - effect, that which is manifest; कार्यम् (kāryam) - the product, result; असत् (asat) - cause, that which is unmanifest; कारणम् (kāraṇam) - the cause; सत् (sat) - the manifest; अभिव्यक्त-रूपत्वात् (abhivyakta-rūpatvāt) - due to its nature of being expressed or visible; कारणम् (kāraṇam) - the cause; च (ca) - and; अपि (api) - also; शब्दितम् (śabditam) - is denoted, described (by the word);]

"'Sat' is the effect; 'Asat' is the cause. Because the manifest is of the nature of expression, the cause too is denoted by the term."

इति ह्यभिधानम्।

iti hyabhidhānam।

[इति (iti) - thus; हि (hi) - indeed; अभिधानम् (abhidhānam) - the expression, the declaration.]

- Thus indeed is the declaration.

"असच्च सच्चैव यद्विश्वं सदसतः परम्॥"

"asacca saccaiva yadviśvaṁ sadasataḥ param॥"

[असत् (asat) - the unmanifest (cause); च (ca) - and; सत् (sat) - the manifest (effect); एव (eva) - indeed; यत् (yat) - which; विश्वम् (viśvam) - the universe; सदसतः (sat-asataḥ) - from both being and non-being (effect and cause); परम् (param) - beyond;]

"That which is the universe, composed of both the unmanifest and manifest, is beyond both cause and effect."

इति च भारते ॥१९॥

iti ca bhārate ॥19॥

[इति (iti) - thus; च (ca) - and; भारते (bhārate) - in the Bhārata (i.e., Mahābhārata);]

- stated thus in the Mahābhārata as well.