These verses give an interesting insight into how far the Israelites may have gone in adding to God's commands about the new moons.
There is a small chance that the new moon in question is the Feast of Trumpets. But if it is not Trumpets, it sets up an interesting situation: As the Israelite's ruling class wallowed in wealth, it drifted farther and farther from a true worship of God. In practicing some stringent traditions that God had nowhere commanded, they had attached their own ideas to His law!
This strict observance did not at all impress God favorably! Totally out of harmony with God's aim of "justice run[ning] down like water, and righteousness like a mighty stream" (Amos 5:24), they missed the intent of God's law entirely! He desires mercy and not sacrifice (Hosea 6:6; Matthew 12:7).
These verses strongly imply that the Israelites did not conduct business during the new moon, but God never commands such a restrictive practice. Clearly, the day was different from common days because of God's assignment of special offerings. But in their occasional bursts of zeal (Romans 10:1-3), the Israelites apparently believed that if the little God required of them was good, then more would be better!