הלכה על ברכות 43:31

A nida (a woman who has menstruated and not yet purified herself by going to the mikveh) is obligated to recite all the berakhot and prayers and may study Torah, for words of Torah cannot become impure, as it is written: “Indeed, My word is like fire” (Yirmiyahu 23:29). Just like fire cannot become impure, the words of Torah do not contract impurity (Berakhot 22a).