What do we learn from "Orach Chayim Pen Tefales"?
Rashi (from Yerushalmi Pe'ah 1:1): Hashem hid the reward of Mitzvos, lest one cling to Mitzvos with a great reward and abandon other Mitzvos. One should not weigh ways of the Torah, which to take and which to abandon.
Rashi: Based on the coming verses, it seems that we still discuss a Zonah. Do not weigh which of her ways to do. Her paths bring to She'ol, and you will not know to beware until you fall in!
Malbim: Ma'agal is a roundabout path. Peles is the Midah to measure and gauge the roundabout Ma'agal in order to get to straightness. Lest you want to go on a roundabout path by the Zonah's house, and weigh how to return to the straight path, e.g. 'let us pass by the house of Zonos and overcome our desire, and receive reward' (Avodah Zarah 17b) - therefore, it says "Na'u Mageloseha Lo Seda." Her paths are pleasant and depart from the straight path, and you will not know how to return to the path of life.
Malbim (according to Melitzah): Do not say that via investigation and philosophy you will return to Emunah, to clarify everything via proofs. Afterwards your Nefesh will go on roundabout paths of doubts, and you will not find the true path in the light of Emunah.
Why does it say "Na'u Mageloseha Lo Seda"?
Refer to 5:6:1:2-3.
