It is laid down that they should have similar hearts and should be each other's friends. For such friendship between Brahmana and Kshatriya, the subjects become happy.
परस्परस्य सुहृदौ विहितौ समचेतसौ। ब्रह्मक्षत्रस्य सम्मानात् प्रजा सुखमवाप्नुयात्॥