The staff of life
Definition 1 of 1
Pro Tip 1/3Metaphoric Use
Understand that 'the staff of life' is often used metaphorically to indicate something vitally important. 
For avid readers, books are the staff of life.
Pro Tip 2/3Cultural Significance
Remember that 'the staff of life' can allude to cultural importance, often reflecting a society's staples or necessities. 
In Italy, pasta is considered the staff of life.
Pro Tip 3/3Non-literal Meaning
Don't take 'the staff of life' literally; it's not always about physical food but what's essential for well-being. 
Friendship, to many, is the staff of life.