B.G 9.19
तपाम्यहमहं वर्षं निगृह्णाम्युत्सृजामि च। अमृतं चैव मृत्युश्च सदसच्चाहमर्जुन ॥१९॥
tapāmyahamahaṁ varṣaṁ nigr̥hṇāmyutsr̥jāmi ca। amr̥taṁ caiva mr̥tyuśca sadasaccāhamarjuna ॥19॥
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.
"'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."
- Thus indeed is the declaration.
"That which is the universe, composed of both the unmanifest and manifest, is beyond both cause and effect."
- stated thus in the Mahābhārata as well.
Gīta Tātparya 9.19