כִּֽי־קָצַ֥ר הַמַּצָּ֖ע מֵֽהִשְׂתָּרֵ֑עַ וְהַמַּסֵּכָ֥ה צָ֖רָה כְּהִתְכַּנֵּֽס׃
For the bed is too short for a man to stretch himself; And the covering too narrow when he gathereth himself up.
Rashi on Isaiah
For the bed is too short for one to stretch When I bring the enemy upon you, he shall press you so that you will not be able to supply his work. When he spreads out his bed upon you, it will be too short for the one who lies on it to stretch.
Ibn Ezra on Isaiah
המצע The mattress,29A. V., The bed. which is underneath in the bed.
Rashi on Isaiah
to stretch (מֵהִשְׂתָּרֵעַ) to lengthen one’s limbs, estandejlejjr in O.F.