Śatapatha Brāhmaṇa ("of a hundred paths") 4.3.3.11

4.3.3.11

apakramādu haivaiṣāmetadbibhayāṃ cakāra | yadime mannāpakrāmeyuryannānyaddhriyeranniti tānevaitadanapakramiṇo 'kuruta tasmādindrāyaiva marutvate gṛhṇīyānnāpi marudbhyaḥ

But he was afraid of their desertion,--'Lest they should desert me, lest they should take to some other (party),' so thinking, he by that (share in the libation) made them unwilling to desert him. This is why he should draw the grahas for Indra Marutvat.