Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
source [sɔːs] n (also fig) исто́чник
I have it from a reliable source that ... у меня́ есть све́дения из надёжного исто́чника, что ...
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.