As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle your library.
The sacrifice of a land is part of the cost of casting Harrow. You can’t pay this cost more than once to get a multiple effect.
The two lands do not count toward your normal one land you can play each turn.
Because the “search” requires you to find a card with certain characteristics, you don’t have to find the card if you don’t want to.