Tafseer Ibn Kathir of AR RA'D [21]

وَالَّذِينَ يَصِلُونَ مَا أَمَرَ اللّهُ بِهِ أَن يُوصَلَ وَيَخْشَوْنَ رَبَّهُمْ وَيَخَافُونَ سُوءَ الحِسَابِ

And those who join that which Allah has ordered to be joined and fear their Lord and are afraid of the evil of [their] account,