Someone told me that mincha is an עת רצון because מידת הרחמים is strongest at that point.
Is there a source for this?
The Shitta Mekubetset to Bava Kamma (82a) (middle of the first paragraph) cites a Gaon that it is an "et ratson". This is found in Otsar HaGeonim Megillah (23b) in the name of R. Sar Shalom Gaon. Tosafot to Pesahim (107a) writes the same. Numerous contemporaneous and later sources writes this as well.