on one's knees

例句：

1. 1. She knelt down to prayfor forgiveness.
   她跪下来祈祷宽恕。
2. 2.The old man was on his knees,begging for help.
   老人跪在地上，乞求帮助。
3. 3. The child knelt before the altar, offering aprayer.
   孩子跪在祭坛前，祈祷。