The answer depends on two things more than anything else: who he made the threat to and what his prior record looks like.
On the charge itself, threatening to physically harm someone typically falls under criminal threatening, menacing, or terroristic threats depending on the state. Most of these charges are misdemeanors at the lower end, particularly for a verbal threat without a weapon, without a specific target in a protected category, and without prior escalation. A first offense misdemeanor threatening charge in most jurisdictions carries anywhere from a few days to up to a year in county jail, with probation being a common outcome for someone without a significant prior record.
The situation changes depending on who received the threat. Threatening a law enforcement officer, a judge, a public official, or a protected class of individuals elevates the charge in most states. A threat made in connection with a domestic situation or against a family member can trigger enhanced penalties and protective orders that complicate the resolution significantly.
Prior criminal history is the other major variable. A judge sentencing someone with a clean record on a verbal threat charge has a lot of room to show leniency. A judge looking at a pattern of similar conduct, prior assault charges, or prior threatening behavior has much less reason to.
If this is a first offense with no aggravating factors and no serious prior record, the realistic outcome in most jurisdictions is time served, a fine, probation, or a short jail sentence. The time he has already served waiting on this may cover whatever sentence gets imposed.
He needs an attorney to review the specific charge and his record before any decisions are made.