Will a person be held accountable if he does not help someone in need, and does the ruling differ between one from whom help was requested and one from whom it was not requested?

Whoever is able to help someone in dire need that would lead to their demise, sins by neglecting to help them if it becomes their duty. However, if assistance is not their duty, or if the person is not in such dire need as to cause them harm, then they do not sin by neglecting to help. Helping a Muslim is one of the greatest acts of proximity to Allah, for the Prophet, peace and blessings be upon him, said: "Whoever relieves a believer of a worldly hardship, Allah will relieve him of a hardship on the Day of Resurrection. And whoever eases the difficulty of a debtor, Allah will ease his difficulty in this world and the Hereafter. And whoever covers a Muslim's fault, Allah will cover his fault in this world and the Hereafter. Allah is in the servant's help as long as the servant is in the help of his brother." And he also said: "The best of people are those who are most beneficial to people."