Tell him to stop going to that quack. Antibiotics are absolutely useless against viral infection. This is one of those facts that you can't tell people if they think they know different. They will just stomp off in a snit telling you how they recovered from this or that viral infection after taking antibiotics, as if that proves anything. He recovered in 4 days? Big deal. I got over Delta in two days and I did not take any medication. Thankfully I was double vaccinated by that time so it didn't hit me hard despite my being old. I isolated for 14 days which was the norm then. Any doctor who prescribes antibiotics for a viral infection should have their license revoked.

https://www.fda.gov/drugs/resources-you-drugs/warning-antibiotics-dont-work-viruses-colds-and-flu

https://www.hopkinsmedicine.org/health/wellness-and-prevention/antibiotics

https://www.drugs.com/medical-answers/antibiotics-kill-coronavirus-3534867/