Seneca the Younger Quotes about Gratitude
Let the man, who would be grateful, think of repaying a kindness, even while receiving it.
"Hoyt's New Cyclopedia Of Practical Quotations" by Jehiel Keeler Hoyt, p. 336-37, De Beneficiis, II. 25, 1922.
He who receives a benefit with gratitude, repays the first installment of it.
"On Benefits". Book by Seneca the Younger, 62 AD.