What is the ruling on unpaid, voluntary work if it competes with paid work, and what are the conditions for such work?

If the intention is to compare between self-benefiting acts of worship and acts of worship that benefit others, especially what is required in its time, such as feeding the hungry and treating the sick during disasters, then the latter is better and carries more reward because its benefit extends to others. This is supported by the Prophet's (peace be upon him) saying: "Every Muslim must give charity." It was asked: "What if he does not find anything?" He replied: "He works with his hands benefiting himself and giving in charity." It was asked: "What if he cannot?" He replied: "He helps the needy person in distress." It was said to him: "What if he cannot?" He replied: "He enjoins good or righteousness." He was asked: "What if he does not do that?" He replied: "He refrains from evil, for it is charity." (Agreed upon). And his saying: "Those who broke their fast today have taken the reward." (Narrated by Al-Bukhari and Muslim), meaning that they attained a full reward for their action that benefited others. Charitable work is not limited to humans but includes every living being, and it has no conditions other than seeking reward and sincerity.