The hybridisation of Fe is K _ 3 [ Fe ( CN ) _ 6 ] is

Electronic configuration of $Fe = [ Ar ] 4s^{2}3d^{6} {Fe}^{2 +} = [ Ar ] 3d^{6}$

${CN}^{-}$ are strong field ligands

$d^{2}{sp}^{3}$ hybridisation

$∵ {CN}^{-}$ is a strong ligand and from six coordinate bonds with ${Fe}^{3 +}$. Thus $Fe$ show $d^{2}{sp}^{3}$ hybridisation in ${K}_{3}Fe ( CN{)}_{6}$.