" take mercy on "

[Idiom]  | "take mercy on" 

1: to treat (someone) kindly

[Noun]  | "mer*cy" | \ ˈmər-sē \

1: compassion, leniency, or restraint (as in imposing punishment) shown especially to an offender or to one subject to the power of another; also : lenient or compassionate treatment

2: imprisonment rather than death imposed as penalty for first-degree murder

3: a blessing that is an act of divine favor or compassion

Origin: 13th century ;

 Middle English, from Anglo-French merci, from Medieval Latin merced-, merces, from Latin, price paid, wages, from merc-, merx merchandise;