The Hebrew word hesed — often translated "lovingkindness" or "steadfast love" — is the closest the Old Testament gets to a single word for loyal love. It is relational, covenantal, and tenacious. It does not quit when the conditions change. God's hesed toward Israel is the backbone of the entire Old Testament narrative — he keeps showing up for a people who keep wandering. That faithfulness is not sentimental; it is structural.
The book of Ruth is one of the most concentrated studies of human loyalty in Scripture. Ruth's declaration to Naomi — "where thou goest I will go" — is not a romantic speech; it is a covenant statement. Ruth is binding herself to a destitute foreign widow with no guarantee of any return. She is enacting hesed toward a woman who told her there was nothing left to hope for. That is loyalty stripped of every incentive except the person themselves.
Jonathan's loyalty to David in 1 Samuel is equally costly. Jonathan was the crown prince of Israel — David was his replacement. He helped David escape the father who wanted him killed. He gave up the kingdom that by birth was his in order to keep his word to his friend. The text says his soul was "knit" to David's soul. That is not a political calculation; it is covenant love choosing a person over a position.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.