Quran 2:248 Al-Baqarah, ayah 248 of 286

وَقَالَ لَهُمْ نَبِيُّهُمْ إِنَّ ءَايَةَ مُلْكِهِۦٓ أَن يَأْتِيَكُمُ ٱلتَّابُوتُ فِيهِ سَكِينَةٌ مِّن رَّبِّكُمْ وَبَقِيَّةٌ مِّمَّا تَرَكَ ءَالُ مُوسَىٰ وَءَالُ هَـٰرُونَ تَحْمِلُهُ ٱلْمَلَـٰٓئِكَةُ ۚ إِنَّ فِى ذَٰلِكَ لَـَٔايَةً لَّكُمْ إِن كُنتُم مُّؤْمِنِينَ ۝٢٤٨

2:248 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.