The Five Skandhas

Sariputra,
Form is not other than emptiness,
and emptiness is not other than form;
form is precisely emptiness,
and emptiness is precisely form.
So are sensation, perception,
volition, and consciousness


Remember that the Heart Sutra is part of the much larger Mahaprajnaparamita-sutra, which, for the most part, addresses the nature of emptiness. In most sutras, the Buddha answers the questions of one or more bodhisattvas, disciples, or arhats. In the Mahaprajna-sutra, it is Subhuti, one of the Buddha’s greatest disciples, who is most often addressed. The Heart Sutra is a unique part of the larger sutra that is addressed, instead, to Sariputra, who was considered preeminent among Buddha’s followers in understanding wisdom, while Subhuti was considered foremost in understanding emptiness. Of course, to understand wisdom, one must also have a thorough understanding of emptiness.