The passuk says in this week’s sedrah (Devarim 17:15):
שׂוֹם תָּשִׂים עָלֶיךָ מֶלֶךְ אֲשֶׁר יִבְחַר ה' אֱלֹקֶיךָ בּוֹ מִקֶּרֶב אַחֶיךָ
“You shall surely place over yourself a king whom Hashem will choose from amongst your brothers.”
The gemara in Kesuvos (17a) explains:
שום תשים עליך מלך שתהא אימתו עליך
“’You shall surely place a king over you,’ [this means] that his fear will be over you.”
If someone rebels against the king he is put to death, the Rambam in Hilchos Melachim (3:8) explains that he is killed by the sword:
כל המורד במלך ישראל יש למלך רשות להרגו .. וכן כל המבזה את המלך או המחרפו יש למלך רשות להרגו כשמעי בן גרא ואין למלך רשות להרוג אלא בסייף בלבד
“If someone rebels against a Jewish King then the king is allowed to kill him ... and also if someone insults the king or curses him the king may kill him as with Shimi ben Geira, however the king may only execute by the sword.”
Tosafos in Sanhedrin (36a, d”h Rabbah bar bar Channa) says that that although if beis din decide that someone is chayav misoh then they have to wait till the next day to execute them, however the king may kill someone who rebelled against him on the same day.
Tosafos asks from a gemara later on in Sanhedrin (48b) which implies that there is no difference between beis din’s chiyuv misah and the king’s chiyuv misah in this regard.
The gemara discusses if the estate of someone who is killed for rebelling against the king goes to the king or to his heirs. The gemara brings a proof from the story of kerem Navos that the estate of the person who rebelled against the king goes to the king.
The passuk (Melachim 1, 21:10) says that Izevel advised Achav that he should hire false witnesses to testify against Navos so that Navos would be killed and then Achav would be able to take his vineyard:
וְהוֹשִׁיבוּ שְׁנַיִם אֲנָשִׁים בְּנֵי בְלִיַּעַל נֶגְדּוֹ וִיעִדֻהוּ לֵאמֹר בֵּרַכְתָּ אֱלֹקִים וָמֶלֶךְ וְהוֹצִיאֻהוּ וְסִקְלֻהוּ וְיָמֹת
“Let them place two godless men opposite him (Navos) and they should testify against him saying, ‘You cursed Hashem and the king’, and they should take him out and they should stone him and he should die.”
The gemara says:
בשלמא למאן דאמר נכסיהן למלך היינו דכתיב (מלכים א כא, יג) ברך נבות אלקים ומלך אלא למאן דאמר נכסיהן ליורשין למה לי ומלך
“I can understand that according to the opinion that the estate of the person who rebelled against the king goes to the king, that is why Izevel advised Achav that the false witnesses should say that Navos cursed the king as well as Hashem (since Navos would be killed for rebelling against the king his vineyard would go to the king).
However according to the opinion that the estate of someone who is killed for rebelling against the king goes to his heirs, then even if Navos was killed for cursing the king as well as for cursing Hashem, then anyway his estate would go to his heirs and not to the king.
In that case, why did Izevel ask the witnesses to testify that Naval had cursed both the king as well as Hashem, since anyway the king would not receive the vineyard as a direct consequence of Navos being killed?”
Tosafos asks; if someone who rebels against the king is killed on the same day, then maybe the reason that Izevel hired witnesses to say that Navos had cursed the king as well as Hashem was in order that Navos would be killed straight away before it was found out that the witnesses were lying?
The Ohr Someach (Hilchos Melachim perek 8) answers as follows:
The mishna (Sanhedrin 81a) says:
מי שנתחייב בשתי מיתות בית דין נידון בחמורה
“Someone who is condemned to two death penalties receives the more severe one.”
Therefore, if Navos would be chayav hereg for cursing the king and also be chayav sekilah for cursing Hashem’s name, then he would be executed by stoning. In this case, beis din would have to delay till the next day to execute him because sekilah for cursing Hashem’s name requires beis din to delay the execution till the next day.
Izevel would not have gained an execution through hereg on the same day by saying that Navos cursed the king, because since Navos would be killed by sekilah, this would only be carried out on the next day.
The Ohr Sameach explains that even although the sentence of sekilah for being mored be’malchus for cursing the king would allow Navos to be killed on the same day, nevertheless beis din would not have been allowed to execute Navos on the same day by sekilah since Tosafos says (daf 81, d”h haniskalin) that the difference between delivering a lenient death penalty and a more severe death penalty has the halachah of dinei nephashos.
Just as the delivery of any chiyuv misah requires beis din to wait till the next day in case they think of a reason why the person should not be killed at all, so too extra severity of a chiyuv sekilah over a chiyuv of hereg would require beis din to wait till the next day in case they would think of a reason that the person should only be killed by hereg.
Therefore it would have anyway been necessary to wait overnight for Naval to be killed and Izevel would not have gained him being killed on the same day by saying that he cursed both the king as well as Hashem.