What are "Chalkei Nachal"?
Rashi: They are rocks in the valley.
Radak: When they found a nice smooth rock in the valley, they would serve it. This is like 'he erected a brick to bow to it' (Avodah Zarah 53b). Chalkei is an adjective for a smooth rock, like Chalukei.
Malbim: The time when you will give your portion to the valley - the children to whom you gave birth, that you will slaughter them there.
How is their portion with the rocks?
Rashi: The rocks will be used to stone them.
Radak: It is the opposite of making Hashem their portion - "Hashem Menas Chelki v'Chosi Atah Tomich Gorali" (Tehilim 16:5). It says Chelki and Chelkecha due to the similarity of the words.
Why does it say "Hem Hem Goralecha"?
Rashi: You will grieve over them, for "also to them you poured libations."
Radak: Refer to 57:6:2:2.
Malbim: In your folly, you will think that via this, the gods are in your portion; they will make a Bris with you for slaughtering your children in the valley.
Why does it say "Gam Lahem Shafachta Nesech"?
Malbim: They believed that the children slaughtered to idolatry were elevated to the kingdom of gods, and they poured libations to the dead bodies.
What is the meaning of "ha'Al Eleh Enachem"?
Rashi: Will I retract from doing evil to you [due to them]?! Radak - Enachem is Nif'al, "va'Yinachem Hashem Al ha'Ra'ah" (Shemos 32:14).
