"O children of Adam, We have bestowed upon you clothing to conceal your private parts," meaning: garments, "and as an adornment," meaning: provisions and wealth.
"But the clothing of righteousness"—the nominative case is used based on a future-oriented expression—and the clothing of righteousness is: chastity.
﴿يَا بَنِي آدَمَ قَدْ أَنْزَلْنَا عَلَيْكُم لباساً يواري سواءتكم﴾ يَعْنِي: الثِّيَاب ﴿وريشا﴾ يَعْنِي: الْمَتَاعَ وَالْمَالَ.
﴿وَلِبَاسُ التَّقْوَى﴾ وَالرَّفْعُ عَلَى مَعْنَى كلامٍ مُسْتَقْبَلٍ، ولباس التَّقْوَى: العفاف.
