Halakhah sa Deuteronomio 22:15: Kitzur Shulchan Arukh

While engaged in the marital act, you should think about Torah subjects or other sacred subjects. Even though [during the act itself] it is forbidden to speak words of Torah, thinking about them is permitted and meritorious, for thought is not likened to speech in this case. Even though in filthy alleys it is forbidden to even think about sacred subjects, this is because of the Divine command, "And your camp shall be holy;"⁴Deuteronomy 22:15. but where it is forbidden because of body nakedness, concerning which it is written, ervas davar (unseemingly thing), our Sages of blessed memory inferred from this that speaking davar (words of Torah) is forbidden, but thinking about them is permitted.⁵Maseches Shabbos 150a. the word דָבָר indicates actual speech.