He would be like one who pays a debt with borrowed money, and prays the sunset prayer with two inclinations (instead of the prescribed four, which it is unlawful to cut short, even when travelling), meaning that what he had done was as if he had done nothing, since a debt thus paid is still a debt, and a prayer thus curtailed is valueless.

I testify that ye twain are the most crafty amongst men and jinn, allusion to Koran, lv. 31: “We will settle accounts with you, O ye men and jinn,” lit., ye two heavy, i.e., troublesome, ones.