Adam Clarke on Exodus 32:1

When the people saw that Moses delayed - How long this was before the expiration of the forty days, we cannot tell; but it certainly must have been some considerable time, as the ornaments must be collected, and the calf or ox, after having been founded, must require a considerable time to fashion it with the graving tool; and certainly not more than two or three persons could work on it at once. This work therefore, must have required several days.

The people gathered themselves together - They came in a tumultuous and seditious manner, insisting on having an object of religious worship made for them, as they intended under its direction to return to Egypt. See Act 7:39, Act 7:40.

As for this Moses, the man that brought us up - This seems to be the language of great contempt, and by it we may see the truth of the character given them by Aaron, Exo 32:22, they were set on mischief. It is likely they might have supposed that Moses had perished in the fire, which they saw had invested the top of the mountain into which he went.