1 Samuel 26:17

And Saul knew David’s voice, and said, Is this thy voice, my son David? And David said, It is my voice, my lord, O king.

Cross-reference

1 Samuel 24:8 describes David calling out to Saul after the cave incident — the same pattern of address and recognition as in 26:17.

1 Samuel 24:16 has Saul's identical question 'Is this your voice, my son David?' — nearly verbatim, showing a repeated moment of recognition.