How can I convince my father not to shave his beard?

Shaving the beard is an act of disobedience and a contravention of the prophetic command to let it grow, and it is an imitation of disbelievers, transgressors, and women. When advising parents, follow in the footsteps of Abraham (peace be upon him) by speaking gently, explaining that guidance lies in knowledge, that disobedience is the path of Satan, and that advice stems from fear of Allah's punishment, and respond to ill-treatment with patience and forgiveness. Explain that happiness lies in obeying the prophetic command and that letting the beard grow is an imitation of the Prophet and the righteous, and a sign of masculinity. Utilize booklets or audio and visual materials on the topic, and supplicate frequently for their guidance.