Moses tells the people – See, I have taught you the statutes and the laws as the LORD my God has commanded me (Devarim 4:5). Using this verse, the Talmud asserts that Torah must be taught for free – just as my God has commanded me and taught me for free, so too, Moses explained – I was obligated to teach you for free. Although it is forbidden to collect payment for teaching Torah, it is not forbidden to pay for studying Torah. This is learned from the verse Buy the truth, but do not sell it…(Proverbs 23:23); one must be willing to pay for the truth – Torah – but one is not allowed to sell it, instead it must be given away for free.