What is the ruling on keeping a beard despite its owner being subjected to criticism from those around him and the anger of his mother who abandoned prayer because of it?

You bear no sin for disobeying your mother in an act of disobedience to Allah; rather, it is obligatory upon you to do so. Therefore, supplicate for her and engage her kindly, clarifying that people's fear of adhering to the religion is a fear instilled by Satan, and that adherence is a source of honor, success, victory, security, blessings, and a good life. Pay attention to your appearance in ways that do not contradict the religion, and interact with her kindly. Explain to her that blameworthy extremism is exaggeration that leads to hardship and boredom, and not taking advantage of dispensations or seeking perfection in worship.