In the Book of Esther, it says that the Jews "established and accepted" (the laws of Purim) - קִיְּמוּ וְקִבְּלוּ kimu v'kiblu. Are those two words Biblical Hebrew?
On the most simple level, of course they are Biblical Hebrew, since the Book of Esther is a biblical book. But I don't think it is actually that simple. The two verbs - קים - "fulfill, ratify, preserve", and קבל - "accept, receive" - occur so frequently in post-biblical Hebrew, and so infrequently in biblical Hebrew that I think it makes sense to put them in the category of at least "late Biblical Hebrew" or perhaps to put them in a new category that would cover the transition period.
Let's take a brief look at the history of each of these words.
The verb קים is the piel form of the verb קום - "to stand, stand up, arise". That kal form appears hundreds of times in the Tanach, Besides meaning to stand on one's feet, it can also refer to permanence - "to remain, to be fixed, to be valid". It can also mean "to stand up to someone", "to oppose" or "to attack". From here, we get the noun komimiyut קוממיות - "independence" (which literally means "to stand up straight", but also has the connotation of "standing up for one's rights".)
The piel form, influenced by Aramaic, along with the related hitkayem התקיים - "took place", gives us the adjective kayam קיים - "existing, enduring", and in modern Hebrew the noun kayamut קיימות - "sustainability". In Aramaic, the verb קום is קאם, which was shortened to קאי, further shortened to ka קא, and that even becomes a prefix - ka ק. That prefix is used very frequently in the Talmud before verbs, and while is difficult to define, has a similar meaning to "did" in English.
The root קבל in earlier biblical texts did not mean "receive", but rather "to be opposite", or "before, in front of". From the sense of "opposite" comes the meaning of makbil מקביל - "parallel" or "corresponding", as found in the description of the loops of the tabernacle (Shemot 26:5). As with the previous verb, קבל was also influenced by Aramaic, and so in the later books of the Tanach, came to mean "receive", since a person receiving stands opposite the person giving. From the verb קבל, we get the noun kabala קבלה - meaning "receiving". Zuckermann describes the development of that word here:
Mishnaic Hebrew קבלה [qabbålå], lit. ‘that which is received, tradition’, refers to ‘the doctrines a disciple receives from his master’, ‘oral teachings not recorded in Scripture’. Later, the term becomes associated with a particular type of received tradition, the mystical doctrines known as the Kabbalah.
The ‘Kabbalah’ meaning is still current in Israeli, but the primary sense has been lifted from the religious arena of received doctrine to the commercial world: kabalá means both ‘receipt’ and ‘(hotel) reception’. Israeli שעת קבלה shat kabalá, lit. ‘hour-CONSTR receipt’, means ‘office hour’ and מבחן קבלה mivkhán kabalá, lit. ‘exam:CONSTR receipt’, is ‘entrance exam’.
Is it possible that there was no word for "receive" in earlier biblical books like the Torah? No - there was a word - lakach לקח. Lakach meant both "take" and "receive" and the similarity between those two meanings (with sometimes the only difference being in the thoughts of the person performing the action) makes it occasionally difficult to tell which one the verse meant. (For examples where lakach more likely meant "receive", see Bamidbar 3:50, 5:25; Devarim 26:4).
This multiple meaning of one word is what likely led to the change in a number of words in post-biblical Hebrew. As we saw in this post, lakach (under Akkadian influence) came to mean "to buy"), leaving natal נטל for "take" and kibel קיבל for "receive". The biblical word meaning "to buy" - kana קנה - took on, in post-biblical Hebrew, a more specific sense of "to acquire possession (by a symbolic act)". As this book points out, in Modern Hebrew, lakach and kana returned to their meanings in biblical Hebrew, kibel still has its post biblical sense, and natal is not used frequently any more.
Just as in the story of Esther - it was necessary for the Jews to accept the new laws for them to have full validity, so too with language - the "prescriptive" only becomes established when accepted by the speakers.