The Hebrew word rachamim is the plural form of rechem (H7358, womb), and refers to the deepest form of compassionate love — the kind a mother feels for the child of her womb. It describes a love that is felt in the gut, that moves one to action. Rachamim appears approximately 40 times in the Old Testament, almost always in reference to God's mercy toward His people. It is distinct from chesed (steadfast covenant love) in that it emphasizes the emotional, tender, and almost instinctual dimension of divine love.
God's rachamim is one of the most profound revelations of His character in the Bible. When God reveals His name to Moses, He says: The LORD, the LORD, a God merciful and gracious — where 'merciful' is the Hebrew rachum from the same root (Exodus 34:6). Isaiah uses the most intimate possible comparison: Can a mother forget the baby at her breast and have no compassion on the child she has borne? Though she may forget, I will not forget you! (Isaiah 49:15). This womb-love of God finds its ultimate expression in Christ — who was moved with compassion (the Greek splanchnizomai) for the crowd (Matthew 9:36), using the exact same visceral imagery.