Hesed is the great covenant word of the Old Testament, and English struggles to hold it in one term: it has been rendered mercy, lovingkindness, steadfast love, and faithfulness. It describes love that is loyal — the love that keeps its promises, that shows up again and again, that does not let go. When Psalm 136 repeats twenty-six times for his mercy endureth for ever, the word is hesed.
Hesed is the love God has for his people despite their unfaithfulness — the love Hosea acted out by loving an unfaithful wife. It is behind the promise that God's compassions fail not; they are new every morning. To grasp hesed is to grasp why the believer's security rests not on the strength of our grip on God, but on the strength of his grip on us.
Hesed in Scripture
O give thanks unto the LORD; for he is good: for his mercy endureth for ever.