What is the ruling on stealing money from someone who spends it on unlawful things, in order to meet the needs of the needy? And how does one repent and purify the money?

Repentance for violating the rights of others and committing injustices against them is not complete except by restoring those rights. It is not permissible to take another person's money unless they willingly give it, even if they spend it on unlawful things; in such a case, they should be advised and guided. Your duty is to seek forgiveness, feel remorse, resolve not to return to such an act, and return the money to its owner without informing them that you stole it. It is sufficient to ensure the right is delivered to them.