Charles Ellicott Commentary 1 Samuel 20:36

"And he said unto his lad, Run, find now the arrows which I shoot. And as the lad ran, he shot an arrow beyond him." — 1 Samuel 20:36 (ASV)

He shot an arrow beyond him. —This was the sign agreed on if all was over for David at the court of Saul. Expositors are in a little difficulty, though, here, as only one arrow is mentioned, whereas “three” had to be shot according to the terms of the understanding.

We cannot imagine, as some have suggested, that “Jonathan shortened the affair and shot only once, considering that there was danger in delay,” and that every moment was crucial; had there been such a need for haste, the parting scene would have been cut even shorter. It is better, with Keil, to assume that the “singular” here stands in an indefinite general way, the author not thinking it necessary, after what he had previously said, to state that Jonathan shot three arrows one after another.