There are serial quotes from the Suttas and Jataka-Atthakatha in the generous gift of "Gratitude in the Buddha's Teaching" by Upasaka Mahinda Wijesinghe.
It would be good if detail resources, even links within the given, are added, perceiving the Sangha of the eight direction and their faithful following as recipient.
At the end of each quote is a number, so that not all quotes need to be requoted, like here for example:
“There are two persons who are rare in the world. Which two? First, the one who volunteers to help others selflessly (pubbakari). And second, the one who is grateful (kataññu) and helps in return (katavedi)”.1
1 = http://accesstoinsight.eu/en/tipitaka/sut/an/an02/an02.119.than or AN 2.119
(Note: This has not been told for exchange, stacks, trade or entertainment but as a means for liberation from this wheel.)