He told them to put wax in their ears, so they wouldnt hear the sirens.
Book 12 of the Odyssey.
So that Circe could tell them the warnings of the sea, thus dodging the Sirens.
To put wax in the sailors ears and tie themselves to the ship.
Circe tells Odysseus that he needs to tell his men to bound him to the mast of the ship with rope, and when he asks them to get out, that he be bound even tighter. As for his companions, there ears will be filled with wax.
the underworld
tell them scylla is a bitchhhead
Hermes advises Odysseus to use the herb Moly to resist Circe's enchantments. He tells Odysseus to draw his sword and threaten Circe with harm if she attempts to bewitch him. Finally, he instructs Odysseus to make Circe swear an oath not to harm him before he agrees to her hospitality.
If Odysseus goes to bed with Circe when she first asks, she will 'unman' him, that is, she will cut off his penis. Hermes tells Odysseus to first make Circe swear that she will do him no harm before he sleeps with her.
Not to kill them, which Odysseus warns his men not do to - and which they do anyway to their doom.
The land of the deads
the underworld
with his son