El muerto y el arrimado al tercer día apesta

lit. 'the dead man and the freeloader start to smell on the third day'. After the third day (or after a certain amount of time), a dead man/freeloader start to stink up your home; it means that after a time something/someone starts to become a nuisance. [ex: you let your friend stay over for a couple of day but he ends up staying two months, he's now become a nuisance.]