וַיָּ֣רָץ דָּ֠וִד וַיַּעֲמֹ֨ד אֶל־הַפְּלִשְׁתִּ֜י וַיִּקַּ֣ח אֶת־חַ֠רְבּוֹ וַֽיִּשְׁלְפָ֤הּ מִתַּעְרָהּ֙ וַיְמֹ֣תְתֵ֔הוּ וַיִּכְרָת־בָּ֖הּ אֶת־רֹאשׁ֑וֹ וַיִּרְא֧וּ הַפְּלִשְׁתִּ֛ים כִּֽי־מֵ֥ת גִּבּוֹרָ֖ם וַיָּנֻֽסוּ׃
And David ran, and stood over the Philistine, and took his sword, and drew it out of the sheath thereof, and slew him, and cut off his head therewith. And when the Philistines saw that their mighty man was dead, they fled.
Radak
When my enemies turn back, They stumble and perish at Thy presence. – For all the Philistine armies fled and turned back, as it is written (1 Sam. 17:51): “And when the Philistines saw that their champion was dead they fled.”
Rashi
Elchonon. Dovid.24We know that it was Dovid who killed Golias in Shmuel I, 17:51, consequently this Elchonon must be Dovid.