SB 6.18.69

athendram āha tātāham
 ādityānāṁ bhayāvaham
apatyam icchanty acaraṁ
 vratam etat suduṣkaram
Synonyms: 
atha — thereafter; indram — to Indra; āha — spoke; tāta — dear one; aham — I; ādityānām — to the Ādityas; bhaya-āvaham — fearful; apatyam — a son; icchantī — desiring; acaram — executed; vratam — vow; etat — this; su-duṣkaram — very difficult to perform.
Translation: 
Thereafter, Diti said to Indra: My dear son, I adhered to this difficult vow just to get a son to kill you twelve Ādityas.