Atharvaveda 5.8.9

5.8.9

átrainān indra vr̥trahann ugró mármaṇi vidhya |
átraiváinān abhí tiṣṭhéndra medy àháṃ táva |
ánu tvendrā́ rabhāmahe syā́ma sumatáu táva ||9||

Here, O Indra, Vṛtra-slayer, do thou, formidable, pierce them in the vitals; just here do thou trample upon them; O Indra, thine ally am I; we take hold on thee, O Indra; may we be in thy favor.