The relationship drawn by Kierkegaard between morality, or ethical behavior, and faith is paradoxical and complex. On the one hand, he views questions of ethical behavior as universal, applying to all people. On the other, there are times when a person, out of faith, might violate accepted ethical behavior because of what Kierkegaard describes as the "teleological suspension of the ethical," where faith transcends the moral. The example that he gives in Fear and Trembling is that of Abraham, who was prepared to willingly engage in an unethical act (the sacrifice of his only son Isaac) because he was commanded by God. How could this behavior be understood? Kierkegaard argues that there are times when one's faith forces them to stand against the universal, not as one person (that would be sin) but as an instrument of God's will. Abraham was commanded directly by God, and so his faith in God (which was ultimately justified) dictated that he transcend universal ethics.
Kierkegaard defines the moral as having an end or telos in mind, such as behaving with the goal (or end) of not harming another person, and believes that ethics or morals are universal: we all have roughly the same understanding of good and evil. But a limit of ethics (morality) is its rationality. Kierkegaard therefore writes of “its inability to comprehend the phenomenon of faith.”
Faith, Kierkegaard argues has an irrational, even absurd, edge that doesn't necessarily align with commonsense notions of morality. It pushes the boundaries of the conventional and steps into problematical territory as far as morality is concerned. For example, to put this in a modern context, how would we understand a suicide bomber, willing to kill himself and others, because he believes it is God's command that he do so? Likewise, how could Abraham be fully willing, if unhappily so, to kill his son Isaac at God's command? There are times when faith demands something beyond conventional ethics, and it is this tension that Kierkegaard examines, refusing merely to tame or domesticate the faith experience.