בעת ההיא, "at that time,⁠" at the end of the forty days when God was finally mollified and said: "carve for yourself!⁠"

ועשית לך ארון עץ, "and make a wooden ark for yourself!⁠". Moses reports that he first made the ark (compare verse 3) and only after that did he carve out the Tablets. He followed this sequence in order to have a "home" ready for the Tablets when he would return with them from the mountain. If he had not first made the ark where would he put the Tablets when he arrived among the people with them? Our sages have a tradition that the "ark" mentioned by Moses in verse 5 was the one that he had made immediately after receiving the instructions to carve out the second set of Tablets. In other words, this was not the same Ark which Betzalel was instructed to make for the Tabernacle in Exodus 25,10 (based on Tanchuma Eikev 10).
The ark which Moses made was strictly temporary in order to have a place for the Tablets to be put pending the instructions to build the Tabernacle and to make a permanent home for the Tablets. The wooden ark made by Moses was the ones the people would take with them when they went to war. The Ark made by Betzalel was removed from the Tabernacle (except during the journeys when the Tabernacle itself was dismantled) only at the express command of God when the people marched around Jericho with the priests carrying the Holy Ark in front of them (Joshua 6,12). When, several hundreds of years later, the sons of the High Priest Eli took it upon themselves to take the Holy Ark to war with them against the Philistines, the Ark was captured and the sons of Eli died as a punishment for their high handed action. (Samuel I 4,8 describes that although, initially the Philistines were frightened of the Ark, they fought the Israelites and were victorious, capturing the Ark).
The ark (box) made by Moses contained (initially) both the Tablets and the broken pieces of the original Tablets which Moses had smashed. After Betzalel made the Holy Ark for the Tabernacle the contents of Moses' ark were transferred to it. This is the meaning of Exodus 25,16: "you will place inside the Ark the testimony which I shall give you.⁠" Even though the Talmud in Baba Batra 14 states: "there was nothing inside the Holy Ark except the two Tablets,⁠" this is not to exclude the broken pieces of the first Tablets, as whenever two restrictive clauses are employed consecutively, the meaning is that something additional is meant, in this case the remnants of the first Tablets. This was after the Temple of Solomon had been built. As long as the Tabernacle of Betzalel functioned as the Temple, the Holy Ark contained the second set of Tablets whereas Moses' ark contained the broken pieces of the first set of Tablets. (Compare Tosafot Eyruvin 63. Tosafot base themselves on the verse quoted by the Talmud in Baba Batra which appears in Kings I 8,9.)

I have already mentioned in connection with Exodus 16,32 that the Ark constructed by Betzalel was secreted inside the Temple (of Solomon) together with the bottle of manna and certain other sacred vessels at the instruction of King Yoshiah who hid them under an area of the Sanctuary known as מחילה. There was a special reason why these specific vessels were selected for hiding rather than others. The reason that King Yoshiah hid the Ark rather than most other sacred vessels was twofold; one reason was its superior holy status unmatched by other sacred vessels. Seeing that it was the first of the holy vessels to be constructed, its holiness was greater than the vessels fashioned later. It was perceived as a symbol of the celestial throne. As a result of such considerations it was feared that loss of the Ark would be equivalent to a departure of God's presence from the land of Israel. The king knew that the state of Israel was going to be destroyed by Nevuchadnezzar as the prophets of his time had been threatening this if the people did not return to God wholeheartedly. It was clear to him that the conquerors would capture and take with them the holy vessels of the Temple to Babylon; this is why he was so concerned with the honour of the Holy Ark that he preferred to bury it and hide it.
The second reason was that the Holy Ark symbolized for him the journeys of the Jewish people. He experienced that the staves of the Holy Ark which protruded a long distance beyond either corner to enable it to be carried. [It was very heavy due to the outer and inner layer of solid gold plus the weight of the Stone Tablets. I have seen a calculation of the total weight of the Ark complete with contents in Eliyahu Ki Tov's commentary on Parshat Terumah or Tetzaveh. If my memory does not deceive me the weight approximated 3 tons. (76,000 lbs) Ed.]
During the reign of King Yoshiah these staves became visibly shorter, making transportation by means of them impossible. They reverted to the size they had been in Moses' time. The king viewed this as a bad omen. Originally, the staves could be seen protruding through the dividing curtain of the Sanctuary from the Holy of Holies by causing the curtain to protrude into the airspace of the Sanctuary where it was pushed by these staves. The retraction in the length of these staves meant for King Yoshiah that the Ark was once more destined to travel, just as in the days of Moses. The Israelites, when looking into the open doors of the Sanctuary, could no longer perceive the curtain bulge at the point they were used to see it do so.
The king also saw that when the High Priest Chilkiyah came to perform the service in the Sanctuary (Kings II 22,8) that he found a Torah scroll on the side of the Holy Ark which had rolled into the Sanctuary instead of remaining in its assigned place in the Holy of Holies on top of the Ark (compare Deut. 31,26 and Talmud Baba Batra 14). These occurrences meant for him that the Temple would be destroyed. This is the reason why Targum Yonathan renders Ezekiel 1,1 "it was in the thirtieth year" as a reference to the year that Chilkiyah found the Torah scroll we mentioned. When considering these various omens King Yoshiah decided to hide the Holy Ark so that it would not have to travel into captivity.
We have established that the sanctity associated with the Ark applied to the Ark made by Betzalel, not the box made by Moses to accommodate the Tablets when he would come down from the mountain many months before the Tabernacle had been erected. Moses' "ark" was strictly a temporary housing for the Tablets pending the construction of the Tabernacle. Concerning the Ark constructed by Betzalel, the Talmud in Eiruvin 63 taught that whenever the Ark and therefore the Presence of the Shechinah were not in their assigned abodes the Israelites were forbidden to engage in marital relations with their wives. It is totally impossible to understand this statement of the Talmud as applying to the ark made by Moses, i.e. the ark that went to war with the people. Seeing that the Holy Ark was held in captivity by the Philistines for seven months (Samuel I 6,1), we cannot assume that during all this time the people did not practice the commandment to be fruitful and to multiply. [I do not understand the author here. He had previously accused the sons of Eli of taking Betzalel's Ark to war without God's authorization although normally only Moses' ark would be taken to war. Moreover, note that in Samuel I 4, it is clear that it was not Moses' ark the people took to war on that occasion. Ed.]
David is also reported to tell Uriah (Bat Sheva's first husband) to go home and engage in marital relations, all of this while war was in progress (Samuel II 11,8). Surely the prohibition mentioned in the Talmud could have applied only to the Ark of Betzalel. The lesson the sages taught must have been "When the HOLY ARK was not 'at home,' i.e. God was not at home, how could the people feel "at home,⁠" by indulging in marital relations and carry on "business as usual!⁠"