क्षत्येवंविद्ध वै ब्रह्मा यज्ञं यजमानं सर्वा- श्चर्त्विजोऽभिरक्षति तस्मादेवंविदमेव ब्रह्माणं कुर्वीत नानेवंविदं नानेवंविदम् ॥
In plain words
By virtue of his knowledge, the Brahman priest truly protects the sacrifice, the patron, and all the attending priests. Therefore, one should appoint only a priest who has this knowledge to the office of Brahman, and never one who lacks it—never one who lacks it.
Close to the Sanskrit
Protecting from harm, the Brahman priest indeed thoroughly protects the sacrifice, the patron, and all the priests; therefore one should appoint only a priest knowing thus as Brahman, not one not knowing thus, not one not knowing thus.