It is narrated from Sayyiduna Shaddad bin Aws (may Allah be pleased with him) that one day he began to weep. Someone asked him the reason for his weeping, so he replied: I remembered something I heard from the Prophet (peace and blessings be upon him), and that is what made me weep. I heard the Prophet (peace and blessings be upon him) say: I fear for my Ummah from shirk and hidden desires. I asked, O Messenger of Allah! Will your Ummah commit shirk after you? The Prophet (peace and blessings be upon him) said: Yes! But they will not worship the moon, the sun, stones, or idols; rather, they will perform their deeds for show (riya). And as for hidden desires, it means that a person keeps a fast, then a desire comes before him, and because of it, he breaks his fast.