Surat Al-Baqara (The Cow) - البقرة

وَقَالَ لَهُمْ نَبِيُّهُمْ إِنَّ ءَايَةَ مُلْكِهِۦٓ أَن يَأْتِيَكُمُ ٱلتَّابُوتُ فِيهِ سَكِينَةٌ مِّن رَّبِّكُمْ وَبَقِيَّةٌ مِّمَّا تَرَكَ ءَالُ مُوسَىٰ وَءَالُ هَٰرُونَ تَحْمِلُهُ ٱلْمَلَٰٓئِكَةُ إِنَّ فِى ذَٰلِكَ لَءَايَةً لَّكُمْ إِن كُنتُم مُّؤْمِنِينَ ﴿٢٤٨﴾

And the prophet said to them: Surely the sign of His kingdom is, that there shall come to you the chest in which there is tranquillity from your Lord and residue of the relics of what the children of Musa and the children of Haroun have left, the angels bearing it; most surely there is a sign in this for those who believe.