Slave trading

“It is forbidden you to trade in slaves, be they men or women. It is not for him who is himself a servant to buy another of God's servants, and this hath been prohibited in His Holy Tablet. Thus, by His mercy, hath the commandment been recorded by the Pen of justice. Let no man exalt himself above another; all are but bondslaves before the Lord, and all exemplify the truth that there is none other God but Him. He, verily, is the All-Wise, Whose wisdom encompasseth all things.” ¹

"QUESTION: Concerning the verse: "he who would take into his service a maid may do so with propriety."
"ANSWER: This is solely for service such as is performed by any other class of servants, be they young or old, in exchange for wages; such a maiden is free to choose a husband at whatever time she pleaseth, for it is forbidden either that women should be purchased, or that a man should have more wives than two." ²