He replied: "Pragâpati (the lord of creatures) was desirous of creatures (pragâh). He performed penance, and having performed penance, he produces a pair, matter (rayi) and spirit (prâna), thinking that they together should produce creatures for him in many ways.

In plain words: The sage Pippalada answers that Prajapati, the lord of all creatures, wanted to make living beings. He did hard spiritual practice and then made a pair: matter (rayi) and life-force (prana), so that together they could produce all creatures.