Chapter IV Sloka 35

yJ}aTva n punmaeRhmev< yaSyis pa{fv, 
yen -UtaNyze;ai[ ySyaTmNywae miy.

yajjtv na punarmoham
eva ysyasi pava | 
yena bhtnyaei 
drakyasytmanyatho mayi ( 4|35)||

Knowing that thou shalt not, O Arjuna, again get deluded like this; and by that thou shalt see all beings in they Self and also in Me.
Commentary:

The knowledge of the Self mentioned in the previous verse is to be learnt from the Brahmanishtha Guru through prostration, questioning and service. When you acquire this knowledge you will not be again subject to confusion or error. You will behold that underlying basic unity. You will behold or directly cognize through internal experience or intuition that all beings from the Creator down to a blade of grass exist in your own Self and also in Me. ( Cf. IX. 15; XVIII. 20)