expression, noun
light in the darkness; godsend; guiding beacon
Metaphorical set phrase for something or someone that brings hope, relief, or guidance in a desperate situation. Often used in literary or rhetorical contexts.
彼の助言は、まさに闇夜の灯火だった。
His advice was truly a light in the darkness.
この一冊の本
This one book became a guiding beacon for me.