The term moral obligation has a number of meanings in moral philosophy, in religion, and in layman's terms.
Generally speaking, when someone says of an act that it is a "moral obligation," they refer to a belief that the act is one prescribed by their set of values.
Moralphilosophers differ as to the origin of moral obligation, and whether such obligations are external to the agent (that is, are, in some sense, objective and applicable to all agents) or are internal (that is, are based on the agent's personal desires, upbringing, conscience, and so on).
These principles were put forth as fundamental underpinnings inherent in the acceptance and practice of Judaism.
This principle is also rejected by most Reconstructionist Jews, but for a different reason; most posit that God is not a being with a will; thus they maintain that no will can be revealed.
Underlying the practice of the Law was assuredly the recognition of certain fundamental principles, he asserted, culminating in the belief in God and revelation, and likewise in the doctrine of divine justice.