וַיִּפְגַּ֨ע בַּמָּק֜וֹם וַיָּ֤לֶן שָׁם֙ כִּי־בָ֣א הַשֶּׁ֔מֶשׁ וַיִּקַּח֙ מֵאַבְנֵ֣י הַמָּק֔וֹם וַיָּ֖שֶׂם מְרַֽאֲשֹׁתָ֑יו וַיִּשְׁכַּ֖ב בַּמָּק֥וֹם הַהֽוּא׃
And he lighted upon the place, and tarried there all night, because the sun was set; and he took one of the stones of the place, and put it under his head, and lay down in that place to sleep.
Pri HaAretz
It is written in the Midrash "Taking one of the stones of that place", in the beginning there were many stones and for Jacob they became one stone. And it is therefore said "[Jacob] took the stone" (see there).
Rashi on Genesis
ויפגע במקום AND HE LIGHTED UPON THE PLACE — Scripture does not mention which place, but by writing בַּמָקוֹם the place it refers to the place mentioned already in another passage, viz., Mount Moriah of which it is stated (Genesis 22:4) “And he saw the place (המקום) afar off”.
Rashbam on Genesis
ויפגע במקום, on his way he had an encounter in or near a town known as Luz.