Al-Baqara 2:248

Their prophet further said to them: “The sign of his kingship is that the Ark will come to you – carried by the angels – having therein tranquility[138] from your Lord and remains of what the House of Moses and the House of Aaron had left. Indeed, there is a sign in this for you, if you are true believers.”

[138] i.e., was giving reassurance.

And their prophet said to them, "Indeed, a sign of his kingship is that the chest will come to you in which is assurance[97] from your Lord and a remnant of what the family of Moses and the family of Aaron had left, carried by the angels. Indeed in that is a sign for you, if you are believers."

[97] Signs giving reassurance.

248. And their Prophet (Samuel عليه السلام) said to them: Verily! The sign of His kingdom is that there shall come to you At-Tâbût (a wooden box), wherein is Sakînah [65] (peace and reassurance) from your Lord and a remnant of that which Mûsâ (Moses) and Hârûn (Aaron) left behind, carried by the angels. Verily, in this is a sign for you if you are indeed believers.

[65] (V.2:248) Narrated Al-Barâ’: A man was reciting Sûrah Al-Kahf and his horse was tied with two ropes beside him. A cloud came down and spread over that man, and it kept on coming closer and closer to him till his horse started jumping (as if afraid of something). When it was morning, the man came to the Prophet صلى الله عليه وسلم and told him of that experience. The Prophet صلى الله عليه وسلم said, "That was As-Sakînah (tranquillity or peace and reassurance along with angels), which descended because of (the recitation of) the Qur’ân." (Sahih Al-Bukhâri, Vol. 6, Hadîth No.531).

And their Prophet said unto them: Lo! the token of his kingdom is that there shall come unto you the ark wherein is peace of reassurance from your Lord, and a remnant of that which the house of Moses and the house of Aaron left behind, the angels bearing it. Lo! herein shall be a token for you if (in truth) ye are believers.