זָכַךְ zâkak (H2141)

to be transparent or clean (phys. or morally)

1) to be pure, be bright, be clean, be bright, clean 1a) (Qal) 1a1) to be bright, be shining 1a2) to be clean, be pure 1b) (Hiphil) to cleanse, make cleanse, make clean

a primitive root (compare זָכָה (H2135));