What is the "beard patrol?" What does Farid caution Amir about?

There is "beard patrol," where the Taliban search for men who are clean-shaven, a criminal offence the guide warns Armir. To find Sohrab without being detected Amir wears a fake beard and long robes, not the western clothes of his youth.

Farid calls them the “Beard Patrol” as they approach in their red pickup truck. His meaning is double: the term describes the Taliban men, who are all bearded, but it also describes what they are doing, which among other things is to literally make sure that all men have beards. In Islam’s holy texts, men are instructed to let their beards grow to distinguish them from followers of other religions. According to the Taliban, a man who shaves his beard is committing a sin, and they make it their job to punish any person caught sinning. Shaving was one of many illegal acts under the Taliban, which is why Amir bought a fake beard before entering the country. The Taliban also prohibited women from working, which the director of the orphanage, Zaman, says is part of the reason there were so many children there. When Afghan men died during the wars, their wives were left to care for their children. But since the women could not work, they had no way to feed the kids. Rather than watch them starve, they would leave them with orphanages.