What was brought close?
Malbim: They put their hearts close to each other, i.e. each revealed his hidden thoughts and secrets when they ambushed to kill the king.
What is the comparison to an oven?
Rashi: They prepared their hearts in an act of ambush, like an oven that is prepared and fired to bake.
Radak: Their heart, which burns like an oven, they brought it close [to fulfillment] in their ambush. They set their hearts to think how to do the evil. One who wants to plunder and steal, first he waits in ambush, so they will not guard from him. The intent is in the ambush.
Malbim: Their heart is like an oven prepared to be heated via flames.
Who slept the entire night?
Rashi: The baker, who fires the oven. After they prepared their hearts and plotted how to do their evil, they sleep until morning.
Radak: The heart is the Kli of thought. A Mashal for the power that acts in it is a baker. A baker fires an oven at night, and in the morning he finds that the wood burned and he bakes the bread, which is the purpose of heating it. He sleeps at night after putting the wood inside ? he has nothing to do until morning. In the Nimshal, the power of Machshavah sleeps at night ? the intent will not be carried out until morning. Thinking is called sleeping, for it does not weary the body.
Malbim: They did not arouse their lust for Arayos that night. They engaged only in rebellion and murder.
What burns in the morning?
Rashi: In the morning they burn like fire, until they finish (carry out) their evil.
Radak: In the morning they are avid to do the evil that they thought about at night. Those who plot evil "Al Mishkevosam b'Or ha'Boker Ya'asuha Ki Yesh l'El Yadam" (Michah 2:1).
Malbim: In the morning, after they killed the king, the oven (their heart and innards) burned. This was not a fire to bake bread, rather, a flame to consume everything near it, from afar. I.e. the power of arousal was not the Yetzer that desires, rather, an angry Ru'ach of Kin'ah, anger and murder.
