King James Version (KJV)
His heart is as firm as a stone; yea, as hard as a piece of the nether millstone.
Modern English
His heart is hard as a stone, hard as the lower millstone.
Hebrew
לִבּ֣וֹ יָצ֣וּק כְּמ֣וֹ אָ֑בֶן וְ֝יָצ֗וּק כְּפֶ֣לַח תַּחְתִּֽית׃
libvo yaṣvq kmvo ʾaben vyaṣvq kpelaḥ taḥtiyt