Bhagavad Gita, Chapter 13, Verse 3

Me do you also know, O descendant of Bharata, to be Kshetrajna in all Kshetras. The knowledge of Kshetra and Kshetrajna is considered by Me to be the knowledge.

Knowing one's own field isn't enough here, real, complete knowledge includes recognizing the source that knows every field.

Krishna extends the earlier definition, naming himself as the knower of every field, not just this one body's. Real knowledge is described as needing that wider recognition too.