“Moses said to the Jews: Look! God has selected someone to build a Temple for you, and that is Betzalel, the grandson of Chur.”
Chur was the person whom the Jews had killed just a few days before for protesting against the worshipping of the Golden Calf. When Aaron saw the murder, he reasoned that he too might be killed, and made a Golden Calf. Now Chur's grandson, a boy of thirteen, was called upon not to avenge, but to gain forgiveness.
That is why Moses said, “Look!” - it will be a sign for you, a remembrance, that the son of the man whom you killed will be building a Temple to bring you forgiveness. The only way for you can achieve forgiveness is if the prosecutor becomes your defender. No further progenitor of Betzalel is mentioned, to emphasize this. Gold is mentioned before silver in all descriptions of the Temple to remind the Jews about the Golden Calf, even though everywhere else silver comes before gold, “Mine is silver and mine is gold, say God.”
In the future the Jews were to worship the Golden Calf yet again, in the time of Yeravam, in the portion of Dan, and Betzalel's helper, Oholiav from the tribe of Dan, was toiling to obtain forgiveness for them before this second worship occurred, in keeping with the rule that God creates a cure before the disease
Art: Honoré Daumier - The Defender