चलती चक्की देख के दिया कबीरा रोइ
दोउ पाटन के बीच में साबुत बचा न कोई
Kabir says that as he looked at the millstones grinding, he wept. All who are caught between the two stones are crushed.
We are caught in the millstones of dualities, birth and death, sin and virtue, love and hate, pleasure and pain among others. Careful examination will reveal that we are immersed in them, thus we are not truly free. We attain freedom (moksha) by transcending the dualities and realizing our UNITY with God and all existence. In the physical millstones, the grains that remain near the post (peg) are not crushed. The post represents God and the grains near it are the people who realized freedom.