Atharvaveda 11.3.40

11.3.40

[4.9]a) tátaś cainam anyéna pr̥ṣṭhéna prā́śīr yéna caitáṃ pū́rva ŕ̥ṣayaḥ prā́śnan |
[4.9]b) vidyút tvā haniṣyatī́ty enam āha |
[4.9]c) táṃ vā́ aháṃ nā́rvā́ñcaṃ ná párāñcaṃ ná pratyáñcam |
[4.9]d) divā́ pr̥ṣṭhéna |
[4.9]e) ténainaṃ prā́śiṣaṃ ténainam ajīgamam |
[4.9]f) eṣá vā́ odanáḥ sárvāṅgaḥ sárvaparuḥ sárvatanūḥ |
[4.9]g) sárvāṅga evá sárvaparuḥ sárvatanūḥ sáṃ bhavati yá eváṃ véda ||40|| [9]

If thou hast eaten it with another back than that with which the ancient seers ate this, the lightning will slay thee: thus one says to him; it verily [have] I not [eaten] coming hither, nor retiring, nor coming on; with the sky as back, therewith have I etc. etc.