Karika 35

सान्तःकरणा बुद्धिः सर्वं विषयमवगाहते यस्मात्। तस्मात् त्रिविधं करणं द्वारि द्वाराणि शेषाणि ॥३५॥

sāntaḥkaraṇā buddhiḥ sarvaṁ viṣayamavagāhatē yasmāt। tasmāt trividhaṁ karaṇaṁ dvāri dvārāṇi śēṣāṇi ॥35॥

[स अन्तःकरणा बुद्धिः सर्वं विषयन् अवगाहते यस्मात्। तस्मात् त्रि विधं करणं द्वारि द्वाराणि शेषाणि॥
sa = together; antaḥkaraṇā = internal instruments buddhiḥ = along with intelligence; sarvaṁ= all; viṣayan = topics; avagāhatē = comprehends; yasmāt = as it is fed; tasmāt = so; tri vidhaṁ = three types of; karaṇaṁ = instruments; dvāri = are like gates; dvārāṇi = off the gates; śēṣāṇi = for the remaining / to the rest of;]

Intelligence along with other internal instruments comprehends all the subjects as it is fed. So, the three types of instruments are like main gates to the rest of the remaining gates.

The intellect, the ego and the mind are the three instruments that are the main gates.