SB 6.18.38

niśamya tad-vaco vipro
 vimanāḥ paryatapyata
aho adharmaḥ sumahān
 adya me samupasthitaḥ
niśamya — hearing; tat-vacaḥ — her words; vipraḥ — the brāhmaṇa; vimanāḥ — aggrieved; paryatapyata — lamented; aho — alas; adharmaḥ — impiety; su-mahān — very great; adya — today; me — upon me; samupasthitaḥ — has come.
Upon hearing Diti’s request, Kaśyapa Muni was very much aggrieved. “Alas,” he lamented, “now I face the danger of the impious act of killing Indra.”

Although Kaśyapa Muni was eager to fulfill the desire of his wife Diti, when he heard that she wanted a son to kill Indra his jubilation was immediately reduced to nothing because he was averse to the idea.