Rashi (from Yalkut Shimoni 277): It is Molech. It was of copper, and they heat it from underneath. Its hands were spread out and fired. They put the child on its hands; he is scalded and screams. The priests play drums, lest the father hear his son's screams and his mercy be aroused. It is called Tofes due to the Tupim (drums). The canyon is called Hinom due to Nahamas (the screaming of) the child. Malbim (30) - they did severe Avodos for idolatry!

Rashi: I did not command to offer children for a Korban. "V'Lo Dibarti ¹ " to any of the Nevi'im [to do so]. And when I told Avraham to slaughter his son, "v'Lo Alsah Al Libi" that he would do so. Rather, it was to inform [the world] of his righteousness.

Radak: If I command to burn flesh in front of Me, it is of animals, and not of their children! They burn them to another god, and have no mercy on them, due to their great love of idolatry.

Radak citing Targum Yonasan: I did not command in the Torah.

Radak citing Targum Yonasan: It was not My will. Kovetz Shi'urim (2, Kuntres Divrei Sofrim 1:23): Below, it says "Lo Tzivisi v'Lo Dibarti v'Lo Alsah Al Libi" (19:5). Targum Yonasan is 'I did not command in the Torah, I did not send via My Nevi'im, and I did not want.' These correspond to three levels of Torah - Tzivuy, Dibur, and Hashem's desire, even without Tzivuy or Dibur. All mid'Rabanan laws are based on this; Chazal accorded with Hashem's desire. Also minors, and all creations from the day of their creation, must do His will. Bil'am's evil was indifference to Hashem's will!

Malbim: Do not say that I did not command because I did not think that they would obey. It never crossed My mind; it is repulsive to Me!