In The Lay of the Cid, the author is concerned with the meaning of honor, integrity, and loyalty. In the poem, however, none of the religious groups are upheld as automatically honorable because of their creed. Thus, this not a work of religious disputation or favoritism, but rather an exploration of how the ideals of chivalry can be maintained under the most trying circumstances of war, mistrust, and betrayal. Christians, Jews, and Muslims all come in for criticism. Only when an individual's behavior demonstrates honor, integrity, and loyalty to a standard beyond narrow in-group preferences does it stand out as praiseworthy. Loyalty to one's group is not as meritorious as loyalty to a higher standard of morality that transcends in-group preference, in the moral universe of the poem. In this sense, the idealized morality of the poem would pose at least as much of a challenge to some of the accepted moral standards of the audience as it would conform to them.
The historical context of the poem is not well understood in the West today, as the brutal conquest, repression, and enslavement of the Christians of the Iberian peninsula is not often taught in American schools, for example. Period sources in Arabic, Spanish, and Hebrew refute this glib narrative. The less than favorable treatment of Jews in the poem must be contextualized. The invasion of Spain by the Moors of North Africa was led by an elite of Arab and Syrian Muslims, aided by some Syrian and Yemeni Jews in Spain who helped plan the invasion and opened the city gates to the invaders. As a reward, these Syrian and Yemeni Jews acted as buffer class administering Islamic rule to the prostrate Christians and were resented accordingly. That resentment is reflected in the poem where the moneylenders are betrayed as just repayment for their own betrayal. It should be noted that many Spanish Jews did not take part in this betrayal and had the same dhimmi bottom status as the Christians under the Islamic military occupation. In terms of population, Jews were vastly outnumbered by the native Christians and the colonizing Muslims, and so they play a smaller role in the poem.
The Moors and the Christians are not shown in more favorable light simply for being the main protagonists, much less for their professed faith. The Christian royalty of Castile is shown as split by treasonous fratricide, pride, stubbornness, and an unwillingness to set aside religious differences and accept Moorish allies to confront yet another wave of invaders from the south. The Moors are shown as cruel (they crucify Christian captives on crosses to mock their faith) and are bent on violent conquest. That good Christians, Muslims, and Jews can strive to transcend their narrow in-group preferences and demonstrate loyalty to a higher integrity and code of honor appears to be a central message of the author of El Cid. This integrity and honor can transcend the label of Christian, Muslim, and Jew, and therein lies the hope for a better and more peaceful world.