fervently, zealously, devoutly, ardently
Она и́стово молилась.
She prayed fervently.
Она истово молилась перед иконой каждый вечер
Every evening, she prayed fervently before the icon.
Старик истово верил в свою правоту
The old man fervently believed that he was right.
Он истово трудился на этой работе
He worked with great dedication at this job.
WiktionaryPONSbab.laReverso
