Who knows the source for the following saying please? "There is no evil without good." I have seen Bereshit Rabbah cited without a page number.
Here is what you are referring to: The Jewish teaching that the Evil Inclination is necessary for all achievement. The Midrash says [Genesis Rabbah 9:7] :
Nachman said, in Rav Shmuel's name: “And, behold, it was very good” refers to the Evil Inclination. Can then the Evil Inclination [then] be “very good”? That would be extraordinary!
Yes, [because] without the Evil Inclination, no man would build a house, take a wife, beget a family, and engage in work. So said [King] Solomon [in Ecclesiastes]: “And I saw that all labor and all achievement in work was the result of man's envy and rivalry with his neighbor.” [Eccl. 4:4]
It sounds like what your source is referencing is a teaching from Rav Amei in tractate Shabbat 55a and also in Midrash Rabbah, VaYikra Rabbah 37:1 which says, “There is not death without sin and there are not afflictions without transgression.”
This discussion is talking about those who die without ever sinning and what the source of death and sin is according to the Torah.
For related discussion concerning the relationship of good and evil and their source in Torah see: https://judaism.stackexchange.com/a/130262/7303