The first time? Nothing. It would have been before I could talk.
If you mean “heard with understanding,” I still don’t know, but it would have been at home before I even started Sunday school. There were Bible verses, gospel songs, hymns, and plenty of prayer occasions, not to mention Bible stories, both from storybooks and from extemporaneous retellings. My mother liked to tell stories in her own words: Bible tales, Greek myths, episodes from the storybooks she had read as a child, and even opera plots. Samson, David and Goliath, baby Jesus, Theseus and Ariadne, Atalanta, the Princess and the Goblin, Dorothy Darling, Peter Rabbit, Bluebeard, and Madama Butterfly were all on the menu alongside family history, and I took them all in about equally.
I was taught to say my prayers as soon as I could talk. In our very religious home, no day passed without invoking a member of the Trinity more than once, and everyone had to take a turn.
I was also taken to church by my parents every Sunday, and my relatives were all very liberal with their sermonizing, pretty much at the drop of a hat.
All that practice made me the atheist I am today.