Bhagavad Gita

ಆಶ್ಚರ್ಯವತ್ ಪಶ್ಯತಿ ಕಶ್ಚಿದೇನಂ ಆಶ್ಚರ್ಯವದ್ ವದತಿ ತಥೈವ ಚಾನ್ಯಃ ।
ಆಶ್ಚರ್ಯವಚ್ಚೈನಮನ್ಯಃ ಶೃಣೋತಿ ಶ್ರುತ್ವಾSಪ್ಯೇನಂ ವೇದ ನಚೈವ ಕಶ್ಚಿತ್ ॥೨೯॥
āścaryavat paśyati kaścidenaṃ āścaryavad vadati tathaiva cānyaḥ |
āścaryavaccainamanyaḥ śṛṇoti śrutvāSpyenaṃ veda nacaiva kaścit ||29||

Gist of the sloka:
If anyone who understands this truth, then it’s an amazing event. Another, when he actually realizes it’s even more amazing. If the person is able tell the truth and another can understand it, then it increases the astonishment. Even then, there is none who can understand the Lord and soul completely.
This verse is about Lord and soul. Those who have actually viewed the Lord are rare. They who have done extreme karmas based on truth have got an opportunity to view the Lord, and they would only be astonished, beyond words. They would be unable to describe Him, for He is beyond words.
The universe itself is an astonishing creation. The Lord who created such a place would definitely be beyond astonishment. Therefore, those who have seen him would find it impossible to describe Him.
Even if they try to describe, then for the listeners it would be an astonishment. At the end Lord remains a mystery wrapped in astonishment.
So, would be the soul, who is a light [knowledge] and remains a mysterious thing. To fully describe would be a tough task, given that its brighter than sun but softer than moon rays.
On our own to understand Lord and the soul would be difficult and tough. Hence the need for guidance and who else than the Lord Krishna is the best position to do so. No one can ever know the Lord and soul better than the universal Lord himself.