Running through the profoundly moving Book of Ruth, the megillah (scroll) read in synagogue on Shavuot, is the virtue of chesed. Chesed reverberates through the book’s four short chapters.

The Midrash (Rut Rabba 2:14) notes the leitmotif:

Rabbi Ze’ira said: This scroll contains neither laws of purity and impurity, nor laws regarding that which is prohibited and permitted. For what purpose, then, was it written? To demonstrate how great is the reward received by those who perform chesed.

The precise meaning of chesed in the Bible is hard to pin down and makes for difficult translation. The King James Version, for example, renders the word variously as mercy, kindness, lovingkindness, and goodness, among other terms, depending on the context.

Translating chesed accurately is complicated by its usage over time. In rabbinic and modern Hebrew, chesed means kindness or benevolence.  In the Siddur, for example, chesed and rachamim (mercy) are often used together. But biblical chesed denotes a different idea.

More fundamental and lasting than kindness, chesed in the Bible implies devotion, commitment, and fidelity. Biblical chesed is most frequently coupled with emet, in the sense of faithfulness rather than truth. Based on natural family ties or a covenant between two parties, chesed entails obligations — moral and sometimes contractual — that remain in effect even when one party has temporarily abandoned the other or is deceased.

Of course, biblical chesed is manifested in mercy and kindness. But while mercy is a cherished Jewish value, it is an emotional and often transient response to any suffering, including that of a stranger. A chesed relationship, in contrast, is rooted in a deeper, more reliable bond expressed in not-so-random acts of kindness.

The entire narrative of Ruth is constructed from cycles and epicycles of mutual love and loyalty. Naomi, Ruth, and Boaz are a chesed triangle, and God, though sometimes thinly veiled, moves the drama forward to its moral conclusion (see Feivel Meltzer’s excellent introduction and commentary in Mossad Harav Kook’s Daat Mikra).

Ruth’s loyalty to Naomi represents the constancy of chesed — it survives the severance of formal family ties following the death of Naomi’s son and Ruth’s husband, Machlon. Ruth would not have been blamed for returning to her mother’s home, like her sister-in-law Orpah, instead of following Naomi to a society in which a Moabite widow would be largely unwelcome. But on the road back to Bethlehem, Ruth pledges to Naomi that “only death will part us” (fittingly, that declaration of chesed inspired the nearly identical line from the Anglican wedding vows).

At their first meeting, Boaz returns Ruth’s chesed by providing sustenance with dignity. He instructs his field hands to treat Ruth as an equal, leave grain behind for her to collect, and take great care not to humiliate her. And Boaz finally redeems Ruth by marriage even though he had no such obligation (biblical levirate marriage applies only to the brothers of the deceased). Rather than a gratuitous act of mercy, their marriage was based on mutual chesed. Boaz insists it was Ruth’s devotion to Naomi’s family that brought them together, since she might have pursued a young suitor instead of an aging relative.

The narrative closes with a display of human and divine chesed working in tandem. Ruth and Boaz bear a son who will perpetuate the legacy of Elimelech, Naomi’s late and heirless husband. And chesed takes on an historic dimension when the child is identified as the progenitor of the House of David.

Why, then, do we read Ruth on Shavuot? The simplest explanation has to do with the agricultural season. The key scenes in the story revolve around the summer wheat harvest celebrated on Shavuot. Likewise, on Passover we read the Song of Songs, with its many refrains of springtime.

But, on a deeper level, Passover and Shavuot represent two stages in the covenantal relationship between God and Israel.

As the festival of Israel’s redemption, Passover recalls the love between a young Israel and her redeemer. Song of Songs, in its allegorical reading, is a hymn to that early love.

Aside from its agricultural significance, Shavuot is the anniversary of the covenant at Mount Sinai. The Sages liken the Torah to a marriage contract — like a wedding, Shavuot represents the time when God and Israel became bound to one another. (To commemorate the event, some Sephardic communities read from a ketubah that lists the reciprocal guarantees of “bride” and “groom.”)

If Passover was a betrothal, Shavuot is a marriage — a love transformed into a covenant of chesed.  The most appropriate occasion to read Ruth is on the holiday of chesed.

Both Shavuot and the Book of Ruth are narratives of love and loyalty combined in an irrevocable bond.