Atharvaveda 11.3.35

11.3.35

[4.4]a) tátaś cainam anyéna múkhena prā́śīr yéna caitáṃ pū́rva ŕ̥ṣayaḥ prā́śnan |
[4.4]b) mukhatás te prajā́ mariṣyatī́ty enam āha |
[4.4]c) táṃ vā́ aháṃ nā́rvā́ñcaṃ ná párāñcaṃ ná pratyáñcam |
[4.4]d) bráhmaṇā múkhena |
[4.4]e) ténainaṃ prā́śiṣaṃ ténainam ajīgamam |
[4.4]f) eṣá vā́ odanáḥ sárvāṅgaḥ sárvaparuḥ sárvatanūḥ |
[4.4]g) sárvāṅga evá sárvaparuḥ sárvatanūḥ sáṃ bhavati yá eváṃ véda ||35|| [4]

If thou hast eaten it with another mouth (múkha) than that with which the ancient seers ate this, thy progeny will die from in front (mukhatás): thus one says to him; it verily [have] I not [eaten] coming hither, nor retiring, nor coming on; with bráhman as mouth, therewith have I etc. etc.