John Gill Commentary 1 Kings 21:8

"So she wrote letters in Ahab`s name, and sealed them with his seal, and sent the letters unto the elders and to the nobles that were in his city, [and] that dwelt with Naboth." — 1 Kings 21:8 (ASV)

So she wrote letters in Ahab's name, and sealed them with his
seal
He giving her leave, no doubt, to take his seal; though she might not communicate her scheme to him, lest he should object to it:

and sent the letters to the elders, and to the nobles that were in
his city dwelling with Naboth :
to the chief magistrates of the city of Jezreel, where Naboth dwelt.