This is an excellent question that points out a number of issues on how we understand terms in the original language and therefore how they are then translated into English.
As has been pointed out, this term only occurs twice in the New testament, here in 14:2 (where it is rendered as "mansions" (KJV) or "rooms" (NASB) and later in 14:23 where it is rendered as "abode" (KJV) or "dwelling" (NASB).
Of value here is how did we end up with "mansions" or "rooms" as the rendering and are there any alternatives.
Understanding a term in the Greek New Testament involves a process that is often historical in nature. More could be added but here is a basic list of some of the issues:
- How was the term used in other secular writings at the time of the writing in the New Testament?
- How did ancient translations handle the term from one language to another? An example of this is how it was handled when it moved from Greek to the Latin Vulgate.
- When terms were first being translated from Greek into English, how was the term handled? In many cases this is how did William Tyndale handle the term, since a very large percentage of the English Bible owes its renderings to the work of William Tyndale.
- Have there been any changes or developments in the various lexicons that have developed in the late 19th and throughout the 20th century? Most are unaware of the major changes that came into Bible interpretations through Crenmer's 19th century lexicon and then the significant change that were brought in by Louw and Nida.
- Finally, a translator often chooses a particular choice of one over another based on their theology.
Not all of these issues apply to how μοναὶ is used here in John 14:2
Here is a summary of some of these issues which have come into this term as it is used in the New Testament.
- Ancient secular use of this term was varied as it had a broad range of uses. The TDNT offers the following uses of this term outside the New Testament:
a. “Stay,” “tarrying,” Eur. Tro., 1129; Hdt., I, 94 (opp. ἔξοδος ἐκ τῆς χώρας); Plat. Leg., IX. 856e; Crat., 437b (opp. φορά, movement); Aristot. Phys., III, 5, p. 205a, 17 (opp. κίνησις); Philo Abr., 58: Nothing is higher than God, πρὸς ὃν … μονὴν εὐχέσθω καὶ στάσιν. μονὴν ποιεῖσθαι, “to take up abode,” Jos. Ant., 8, 350; 13, 41; “abiding,” Philo Vit. Mos., I, 316: διὰ τὴν ἔνδον μονήν, I, 64: “persistence,” Plat. Crat., 395a (along with καρτερία); tt. for staying in service as opp. to leaving it, BGU, II, 581, 6 ff. (2nd cent.): ἐγγυᾶσθαι … μονῆς καὶ ἐμφανείας. “Procrastination,” Philo Vit. Mos., I, 330; “continuance,” Polyb., 4, 41, 4 f. (along with στάσις); Philo Som., II, 237; Aet. Mund., 116 (ἀσαλεύτου μονῆς); Vit. Mos., II (III), 125: τὴν διαιωνίζουσαν αὑτῶν μονήν, Spec. Leg., I, 58; “permanence,” 1 Macc. 7:38: μὴ δῷς αὐτοῖς μονήν. b. “Abiding place,” Apc. Pt. Fr. (acc. to Cl. Al.), 2: ἵνα γνώσεως μεταλαβόντα τῆς ἀμείνονος τύχῃ μονῆς, “place of halt” on a journey, “inn,” Paus., X, 31, 7 (mansio), “watch-house” in a police district: E. J. Goodspeed, Greek Papyri from the Cairo Museum (1902), 15, 19, “hut for watching” in a field, P. Masp., 107, 10 (6th cent.).
The range includes places that are temporary in nature to more permanent places of abiding. What is common to many of the uses is the idea of a dwelling place with no particular emphasis on the kind of dwelling place. Especially interesting is the use of this term as a place to halt your journey or an inn. One use of this term is when people travelled along the Roman roads there were a series of inns that were about a days journey between each one that travelers would stay at each night. Those "inns" were referred to as a "μοναὶ."
One ancient source is how Origen handled this term, emphasizing the idea of a series of "stations." The idea was based on his false idea that there would be ranks in heaven as one ascended up the ladder from a lower station to a higher station.
When μοναὶ was translated into Latin it was rendered as mansiones. As one might expect, this became the root of our word "mansion," but that is not how it is used in Latin. In Latin this term means a place to stay or a stopping place.
It was Tyndale who took the Latin term and took the English word that had evolved from the Latin term and placed it into his translation. This is how we get "mansions" in this verse. What makes this even more difficult is that "mansion" had a very different use in the 16th and early 17th century. For example if you look at the 1828 Webster's dictionary the oldest definition is "Any place of residence; a house; a habitation." It is interesting that it also quotes John 14:2 under this definition of the term as as well. Another use was as a "residence." It also described this term as the house of the lord of a manor. The problem is we see the word mansion today and we only think of it as a massive house with many rooms and we insert that meaning into the verse, even though that is not what is meant by the term. The use of "rooms" carries the same imported idea, a large house with many rooms."
What Jesus is saying is that He is going to prepare a dwelling place for us. Not about the kind of room that we might have in heaven. It is that we will be in heaven with Him, not about what that place will look like.
- There is a very interesting interpretation of this verse that is based on a literal interpretation of this verse along with other verses. A first question or point is, what will be our permanent dwelling place for eternity? If we interpret Revelation 21-22 literally, then the new earth will be our permanent dwelling place in the New Jerusalem, and not in heaven. In a pre-millennial eschatology, believers in the church age will be raptured and will meet him in the air to join Him in heaven. There we will remain until after the tribulation, and we will then return to the earth for the literal earthly kingdom known as the millennium. Then the new heavens and the New earth, which is called the eternal state.
This interpretation suggests a very interesting point about John 14:2. This view may suggest that Jesus was using the term in the same way as those who held to the term as a stopping place on a journey. By this Jesus may have been telling us that He was going to prepare a stopping place for us on our journey with Him.
The most important item in this passage is the idea that we will be with Jesus and through that are heart will be settled or our heart will be at rest. Both "mansion" and "rooms" serve to get our mind focused on the place instead of the fact that we will be in the father's house. Therefore after all of that I would render this as a dwelling place or an abode instead of either of the other two.