Rule 702.47a

Splice is a static ability that functions while a card is in your hand. “Splice onto [quality] [cost]” means “You may reveal this card from your hand as you cast a [quality] spell. If you do, that spell gains the text of this card’s rules text and you pay [cost] as an additional cost to cast that spell.” Paying a card’s splice cost follows the rules for paying additional costs in rules 601.2b and 601.2f–h. Example: Since the card with splice remains in the player’s hand, it can later be cast normally or spliced onto another spell. It can even be discarded to pay a “discard a card” cost of the spell it’s spliced onto.