After ad 'to eat' , comes the augment aṭ before a sārvadhātuka affix consisting of a single consonant, according to the opinion of all grammarians.,
As आदत् and आदः ॥ Before a non-aprikta we have अत्ति, अत्सि ॥ The word सर्वेषाम् makes it a necessary rule and not optional, like the last.,