Householder "?? English research institute" quoted:
The three things a buddha can't do (如來 三不能 Buddha's three incapacities) 1.不能免 定業衆生 He cannot destroy bad karma for anyone. 2.不能度 無緣衆生 He cannot save the people unrelated to him. 3.不能盡 衆生界 He cannot save the whole world of all living things
rightly answering here.
For the increase of faith and as possibility to make merits in such (as well as asked by ChrisW in a comment):
Where can this statement be found literary in the basked of the heritage of the Buddhas teachings?
(Note that this is not asked for trade, exchange, stacks, entertainment and akusala deeds, but as a share of merits and continue such for release)