Sutric source for "all beings have been your mother" (mar shes; first point after equanimity in six-fold cause and one effect instruction)...
Mata Sutta: Mother
translated from the Pali by
Thanissaro Bhikkhu
At Savatthi. There the Blessed One said: "From an inconstruable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. A being who has not been your mother at one time in the past is not easy to find... A being who has not been your father... your brother... your sister... your son... your daughter at one time in the past is not easy to find.
"Why is that? From an inconstruable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. Long have you thus experienced stress, experienced pain, experienced loss, swelling the cemeteries — enough to become disenchanted with all fabricated things, enough to become dispassionate, enough to be released."
