Such “holy and lawful laughter” is contagious and inviting. It includes rather than excludes. The inviting and inclusive nature of holy laughter is witnessed in vs. 6, when Sarah notes that “everyone who hears will laugh with me.”
Calvin discovers in Gen. 21, with its record of Isaac’s birth and Ishmael’s banishment from Abraham’s house, a contrast between two kinds of laughter, one “holy and lawful,” the other “canine and profane.” Holy laughter — not (of course) to be confused with the phenomenon of inexplicable giggling that cropped up in certain late-twentieth century charismatic circles of the church — flows from sheer wonder and astonishment at God’s unexpected and undeserved goodness to his people. It is an expression of pious and believing disbelief (as it were); the fruit of recognition that the most appropriate response to “Can it be that I should gain?” is simultaneously “of course not” (given sin) and “yes, I not only can, but already have” (by God’s sheer grace).
In Gen. 21 it is Abraham and Sarah who thus laugh wholly and holily in response to God’s goodness to them. Their laughter is prompted by God’s fulfillment (at last!) of his promise of a child to them. “The Lord visited Sarah as he had said, … and Sarah conceived and bore Abraham a son in his old age” (Gen. 21.1-2). Calvin comments: “Isaac was to his father and others the occasion of holy and lawful laughter; … [he] brought laughter with him from his mother’s womb, since he bore — engraven upon him — the certain token of God’s grace.” The laughter which Isaac engendered in his parents and others finds reflection in his very name: “Isaac” means “laughter.”
Such “holy and lawful laughter” is contagious and inviting. It includes rather than excludes. The inviting and inclusive nature of holy laughter is witnessed in vs. 6, when Sarah notes that “everyone who hears will laugh with me.” It is equally witnessed in vs. 8, when Abraham throws a large party on the occasion of Isaac’s weaning — a context for joyous and grateful laughter by all. “It is not [God’s] design,” Calvin notes on this score, “to prohibit holy men from inviting their friends to a common participation of enjoyment, so that they, jointly giving thanks to God, may feast with greater hilarity than usual.” Of course, Calvin quickly adds, “temperance and sobriety” are always in order. But “God does not deal so austerely with us as not to allow us, sometimes, to entertain our friends liberally.” Calvin goes so far as to note several appropriate occasions for festive “hilarity,” for instance “when children are born to us” or “when nuptials are to be celebrated.” Calvin’s rather blunt endorsement of parties to celebrate births and marriages would no doubt have caused some of his seventeenth-century Scottish heirs some discomfort.
But, of course, not all laughter is holy. “Sarah saw the son of Hagar the Egyptian, whom she had borne to Abraham, laughing. So she said to Abraham, ‘Cast out this slave woman with her son, for the son of this slave woman shall not be heir with my son Isaac'” (Gen. 21.9-10). Sarah’s response to Ishmael’s laughter is harsh, but is not, in Calvin’s judgment, “without cause,” because Ishmael’s laughter was prompted not by joy, but by ridicule and hatred. “Therefore, as an impious mocker, [Ishmael] stands opposed to his brother Isaac…. [Isaac] so exhilarates his father’s house that joy break forth in thanksgiving; but Ishmael, with canine and profane laughter, attempts to destroy that holy joy of faith.” Ishmael’s laughter was thus ultimately an expression of “manifest impiety against God.”
If holy laughter is inclusive, unholy laughter of the kind expressed by Ishmael is exclusive. It is forbidding and divisive, rather than inviting. Ishmael is not among the number laughing “with” Sarah, as she predicted in vs. 6 that some would do. Ishmael is among the number laughing “at” Sarah and her child, and thus he ultimately mocks not only God’s goodness, but God’s peculiar promise and fulfillment of a seed (from which would come the Seed) to Abraham.