C. F. Keil and Franz Delitzsch on 1 Samuel 20:23

1Sa 20:23

This arrangement was to remain an eternal secret between them. “And (as for) the word that we have spoken, I and thou, behold, the Lord is between me and thee for ever,” namely, a witness and judge in case one of us two should break the covenant (vid., Gen 31:48-49). This is implied in the words, without there being any necessity to assume that עד had dropped out of the text. “The word” refers not merely to the sign agreed upon, but to the whole matter, including the renewal of the bond of friendship.

David thereupon concealed himself in the field, whilst Jonathan, as agreed upon, endeavoured to apologize for his absence from the king’s table.