Virtue or Obligation

 'Uthman (radyAllahu'anhu) also said, “There are four things, the outward of which is a virtue but the inner of which is an obligation – being in the company of the righteous is a virtue and imitating them is an obligation; reciting the Qur’an is a virtue and acting according to its commandments is an obligation; visiting the graves is a virtue and preparing for the time when one will enter them is an obligation; visiting a sick person is a virtue and asking him for advice is an obligation.”