The 245th mitzvah is that we are commanded regarding the laws of buying and selling, in other words. the methods in which acquisitions and product sales amongst the purchasers plus the sellers become legally binding.

The Torah taught about one technique in G-d’s statement (exalted be He), “When you sell something to your neighbor, [or buy one thing from your neighbor’s hand…]” Our Sages said, “[The word ‘hand’ teaches that the purchase] refers to something that can pass from a single hand to some other,” in other words. meshichah [physically moving the object].

It really is explained that in Biblical law, transfer of money is adequate to complete the deal, and meshichah is necessary only by Rabbinic decree, as is mesirah [giving the automobile of control, e.g. the reins of a horse, to your buyer] and hagba’ah [lifting the object].

The Gemara explicitly states, “just like our Sages enacted a requirement of meshichah to ensure that a purchase to be valid, therefore too they needed meshichah to help a watchman relationship to become legitimate.” It is clear that the requirement of meshichah in exchanging is of Rabbinic origin, as explained within the relevant spot.

However, other methods of acquiring land, etc., in other words. by means of a document or chazakah are traced to Biblical verses [and are consequently of Biblical, not Rabbinic, origin.

Reference: https://www.chabad.org/library/article_cdo/aid/961606/jewish/Positive-Commandment-245.htm