earnest appeal

Translations
серьезная просьба
They made an earnest appeal for donations.
Они сделали серьезную просьбу о пожертвованиях.
Definitions
An earnest appeal is a sincere and heartfelt request or plea made to someone, often emphasizing the importance or urgency of the matter at hand.
Words
earnest

adjective
искренний
appeal

noun
просьба