In plain words
Knowing that, you will never again fall into such delusion, Pandava; through it you will see all beings without exception in Ātma, and also in Me.
Word for word
Having gained which, you will not again fall into delusion thus, O Pāṇḍava; by which you will see all beings without remainder in the self, and also in Me.
The commentators
Bhagavadgītābhāṣyam
तथा च सति इदमपि समर्थं वचनम् —
यत् ज्ञात्वा यत् ज्ञानं तैः उपदिष्टं अधिगम्य प्राप्य पुनः भूयः मोहम् एवं यथा इदानीं मोहं गतोऽसि पुनः एवं न यास्यसि हे पाण्डव । किञ्च — येन ज्ञानेन भूतानि अशेषेण ब्रह्मादीनि स्तम्बपर्यन्तानि द्रक्ष्यसि साक्षात् आत्मनि प्रत्यगात्मनि ‘मत्संस्थानि इमानि भूतानि’ इति अथो अपि मयि वासुदेवे ‘परमेश्वरे च इमानि’ इति ; क्षेत्रज्ञेश्वरैकत्वं सर्वोपनिषत्प्रसिद्धं द्रक्ष्यसि इत्यर्थः ॥ ३५ ॥
In plain words
And once that is granted, this statement too holds good —
'Knowing which' means: having gained the knowledge taught by them — 'the very delusion you are lost in now, you will never fall into again, son of Pāṇḍu.' And there's more: 'by that knowledge you will see, without exception, every being from Brahmā down to a blade of grass, directly, right within the innermost Self' — 'these beings dwell in Me', and further, 'they dwell in Me, in Vāsudeva, the Supreme Lord.' You will see the very oneness of the individual soul and God that every Upaniṣad establishes. That is the meaning.
Close to the Sanskrit
And that being so, this statement too is well-founded —
'Knowing which' — having attained, having gained, which knowledge taught by them — 'in the way you have now fallen into delusion, never again, in that way, will you go [into it]', O son of Pāṇḍu. Moreover — 'by which knowledge you will see beings without exception, from Brahmā down to a blade of grass, directly in the Self, in the very innermost Self' — 'these beings abide in Me', and further, also, 'these abide in Me, Vāsudeva, the Supreme Lord' — you will see the oneness of the individual soul and the Lord, well established throughout all the Upaniṣads. This is the meaning.
Gītā Vāhini
“కౌంతేయా! జ్ఞానము యొక్క ప్రభావము చేత తొలుత సమస్త భూతములనూ నీ యందు నీవు చూడవలెను. తరువాత నా యందు చూడవలెను. దీని వలన అజ్ఞాన మోహములు తొలగిపోవును. సూర్యోదయము వలన చీకటి అదృశ్యమైనట్లు, జ్ఞానోదయము వలన అజ్ఞానము అదృశ్యమగును.”
In plain words
“Kaunteya! By the power of Jñāna, you must first see all beings in yourself. Then you must see them in Me. By this, Ajñāna and moha will fall away. As darkness vanishes at the rising of the sun, Ajñāna vanishes at the dawning of Jñāna.”