taḥtihā
underneath them
N – genitive noun + PRON – 3rd person feminine singular object pronoun hā
Root Link: ت ح ت
l-anhāru
the rivers
DET – determiner prefix al + N – nominative masculine plural noun
Root Link: ن ه ر
wadhālika
And that
REM – prefixed resumption particle wa + DEM – masculine singular demonstrative pronoun
Root Link: ذ ل ك