I heard Ka`b bin Malik talking after his failure to join (the Ghazwa of) Tabuk. He said, "When I greeted Allah's Messenger (ﷺ) whose face was glittering with happiness, for whenever Allah's Messenger (ﷺ) was happy, his face used to glitter, as if it was a piece of the moon, and we used to recognize it (i.e. his happiness) from his face."