Manava Dharmashastra 3.110

3.110

na brāhmaṇasya tv atithir gṛhe rājanya ucyate
vaiśyaśūdrau sakhā caiva jñātayo gurur eva ca //

But a Kshatriya (who comes) to the house of a Brahmana is not called a guest (atithi), nor a Vaisya, nor a Sudra, nor a personal friend, nor a relative, nor the teacher.