Like as a father pitieth his children, so the LORD pitieth them that fear him.
Like as a father pitieth (his) children, (so) the Lord pitieth ... For he knoweth our frame. The misery of our state, which might seem to shut us out from One so infinitely perfect, is the very inducement to God to show fatherly pity toward us (Psalms 78:38-39; Psalms 89:47).
Our frame - our natural constitution. The same Hebrew ( yitsreenuw (H3336)) is used here as in Genesis 2:7; therefore the allusion is to that passage, 'The Lord God, framed (English version, formed) man of the dust.' He, as being our Framer, knoweth our frame.
He remembereth that we are dust. The Hebrew, ( zaakuwr (H2142)) is passive or reflexive, 'He is mindful,' etc.