They cannot be known at the time of approach but are...

They cannot be known at the time of approach but are recognised at the time of return. They blow like the blowing of winds, striking some cities and missing others. Beware that the worst mischief for you in my view is the mischief of Banu Umayyah, because it is blind and also creates darkness. Its sway is general but its ill effects are for particular people. He who remains clear-sighted in it would be affected by distress, and he who remains blind in it would avoid the distress.

By Allah, you will find Banu Umayyah after me worst people for yourselves, like the old unruly she-camel who bites with its mouth, beats with its fore-legs, kicks with its hind legs and refuses to be milked. They would remain over you till they would leave among you only those who benefit them or those who do not harm them. Their calamity would continue till your seeking help from them would become like the seeking of help by the slave from his master or of the follower from the leader.

We Ahlul Bayt (the Household of the Prophet) are free from this mischief and we are not among those who would engender it.