Solomon lived amidst glory, and all creatures were subjected to him. Then Allah the Exalted ordained for him to die. His life and death were full of wonders and miracles; thus, his death harmonized with his life and glory. His death, like his life, was unique. The people had to learn that the future is known neither by the jinns nor by the prophets, but by Allah alone. Solomon's effort in this direction did not end with his life, for even his death became an example.

He was sitting holding his staff, overseeing the jinns at work in a mine. He died sitting in this position. For a long time no one was aware of his death, for he was seen sitting erect. The jinns continued with their strife and toil, thinking that Solomon was watching over them.

Many days later, a hungry ant began nibbling Solomon's staff. It continued to do so, eating the lower part of the staff, until it fell out of Solomon's hand, and his great body fell to the ground. People hurried to him, realizing that he had died a long time ago and that the jinns did not perceive the unseen, for had the jinns known the unseen, they would not have kept working, thinking that Solomon was alive.

Solomon's Death - Qur'anic
Allah the Exalted revealed: And We caused a fount of (molten) brass to flow for him, and there were jinns that worked in front of him by the Leave of his Lord, and whosoever of them turned aside from Our Command, We shall cause him to taste of the torment of the blazing Fire. They worked for him what he desired, (making) high rooms, images, basins as large as reservoirs, and (making) cauldrons fixed (in their places). 'Work you, 0 family of David, with thanks!" But few of My slaves are grateful.
Then when we decreed death for him (Solomon), nothing informed them (jinns) of his death except a little worm of the earth, which kept (slowly) gnawing a way at his stick, so when he fell down, the jinns saw clearly that if they had known the unseen, they would not have stayed in the humiliating torment. Surah 34: 12-14