大恩不言谢

1. • a mere "thank you" is an insufficient response to a huge favor

     maxim

2. • words cannot express my appreciation for what you have done

     expression of gratitude

Character by character

• 大(dà)big
• 恩(ēn)favor
• 不(bù)no
• 言(yán)words
• 谢(xiè)thank