Exode 25:11

And thou shalt cover it with pure gold within and without, and shalt make upon it a crown of gold round about.

זהב טהור, this does not mean that gold cannot become ritually impure; we know it can become defiled from Numbers 31,22. The expression טהור here means: ”pure, refined.”

וצפית, “you are to cover it;” actually the Holy Ark was meant to be made of pure gold, not merely gold plate. The reason that it was not all gold, was that gold is very heavy and the Holy Ark plus its contents had to be carried on the Levites’ shoulders. [Even as it was, according to a calculation by Rabbi Eliyahu ki tov, the weight was 78000lbs. Ed.] The reader will wonder how a few Levites could possibly carry even such a weight, and having this in mind the Talmud in tractate Sotah folio 35, states that far from the Levites carrying the Ark, the Ark was transporting its carriers. [Especially while the entire nation crossed the river Jordan under the command of Joshua and the Levites carrying the Ark had to position themselves in a manner which would stop the waters of the Jordan flowing south until the last man had crossed.] (Joshua 3,17) Normally, and for brief periods, the Levites were able to carry the Ark, (with G–d’s help, of course, as when Yaakov rolled away a stone that several shepherds had been unable to move as much as an inch.) Our author questions that if carrying the Ark on their shoulders was a command that applied only on a certain occasion, why was Uzza punished when he tried to steady the wagon transporting the Ark. (Chronicles I 13,9-10, as well as Samuel II 6,7) He leaves the question unanswered. [The Talmud there even states that Uzzah went straight to the world to come, as a reward for his noble intention, I suppose. Ed.] Not only the Ark, but also the Table and the “golden” altar were not made of solid gold but their wooden base was overlaid with gold plate both from the outside and the inside. The same applied to the copper altar, which also had to be carried on the shoulders of the Levites during the journeys in the desert. (Compare Exodus 21,1) [This editor sees no contradiction in all this, as until the 40th year in the desert the Israelites lived on miracles, miracle water, miracle bread, clothing that did not wear out, complete protection against heat and cold by special clouds, etc. This only changed partially during the fortieth year when they conquered land, flocks and herds, etc. Presumably, crossing the Jordan river, brought that period to an end, as immediately after that the commandment to set aside challah from dough made from grain that had grown in the Holy Land, became applicable. Ed.]