Instant — Arcane, 5U (6)
Rare
Target permanent's controller sacrifices it. If he or she does, that player reveals cards from the top of his or her library until he or she reveals a permanent card that shares a card type with the sacrificed permanent, puts that card onto the battlefield, then shuffles his or her library.
Splice onto Arcane {2}{U}{U} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)
Illus. Alex Horley-Orlandelli

4/1/2005: When Reweave resolves it uses the type(s) that the permanent had right before it was sacrificed
11/1/2005: The player reveals cards only if the targeted permanent gets sacrificed.
4/1/2008: With the introduction of the Tribal type it became possible for an instant or sorcery card to share a type with the sacrificed permanent (ie, a Tribal Instant card shares a type with a Tribal Enchantment card). Reweave has received errata so that the effect looks for a *permanent* card that shares a type with the sacrificed permanent. A permanent card is a card that could be put onto the battlefield, which is any card that isn't an Instant or Sorcery.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern