Rule 115.7e

When changing targets or choosing new targets for a spell or ability, only the final set of targets is evaluated to determine whether the change is legal. Example: Arc Trail is a sorcery that reads “Arc Trail deals 2 damage to any target and 1 damage to any other target.” The current targets of Arc Trail are Runeclaw Bear and Llanowar Elves, in that order. You cast Redirect, an instant that reads “You may choose new targets for target spell,” targeting Arc Trail. You can change the first target to Llanowar Elves and change the second target to Runeclaw Bear.