pukunui
Legend
This. Sheathing or unsheathing a weapon counts as an interaction with an object, of which you only get one free each turn. Grabbing material spell components, however, doesn't appear to count, so you can sheathe your weapon for free and cast your spell (and move) on round one. Then you can draw your sword as part of an attack you make on the following round. Or, if you've MCed into fighter and have Action Surge, you can draw your sword again as part of your second action on the same round.I would rule that unsheathing the weapon would need to happen as part of the character's action in the following round, as part of a melee attack action. So in a round 1, the paladin sheaths sword and casts a spell with M/S, next round he/she unsheathes and makes a melee attack.