Q:

Not to marry a divorcée

I remember hearing in a daf yomo shiur (and I want to find where is it written) 
something similar to this: it is preferable not to marry a divorced woman (if her ex-husband is still alive) because it might not be good for your future children (since she might be thinking about her first husband, but that if she is a widow then there is no fear of this.)
Please help me find where something like this is written.

A:

It is a gemara in Pesachim 112a which talks about advice from the chachamim (I don't believe this is quoted in the poskim - not sure):

לא תבשל בקדירה שבישל בה חבירך מאי ניהו גרושה בחיי בעלה דאמר מר גרוש שנשא גרושה ארבע דעות במטה ואי בעית אימא אפילו באלמנה לפי
  שאין כל אצבעות שוות

Do not cook in a pot that your friend already cooked in. What does this mean: that a man should not marry a divorcee who's husband is still alive, for Master says a divorced man who marries a divorcee there are 4 minds in the bed, or if you prefer to say that even a widow is a problem since all fingers are not equal (she may think about her previous husband).
See Rashi.

