Manava Dharmashastra 5.99

5.99

vipraḥ śudhyaty apaḥ spṛṣṭvā kṣatriyo vāhanāyudham
vaiśyaḥ pratodaṃ raśmīn vā yaṣṭiṃ śūdraḥ kṛtakriyaḥ //

(At the end of the period of impurity) a Brahmana who has performed the necessary rites, becomes pure by touching water, a Kshatriya by touching the animal on which he rides, and his weapons, a Vaisya by touching his goad or the nose-string (of his oxen), a Sudra by touching his staff.