John Gill Commentary 1 Samuel 20:11

"And Jonathan said unto David, Come, and let us go out into the field. And they went out both of them into the field." — 1 Samuel 20:11 (ASV)

And Jonathan said to David, come, and let us go out into
the field
That they might more fully, and freely, and familiarly talk of this affair between them, without any danger of being overheard by the servants of Saul, as they were in his palace, where they now were:

and they went out both of them into the field ;
which belonged to Gibeah.