The Gemara in Yebamot 117 tries to explain the reciprocity of sentiment between a mother-in-law (X) and her daughter-in-law (Y). As an illustration of this phenomenon, the Gemara quotes a verse in Proverbs (27, 19): "As face answers to face in water, So does one man’s heart to another.". If the Mishna lists X as unfit to testify for Y, there is no need to list Y as unfit to testify for X.
In a Berayta, Rabbi Yehuda attempts to explain each case.
He concludes that this sentence speaks about the Torah's words. Rashi gives two different explanations. The second is: If his teacher "masbir lo panim" he will acquire the wisdom. If not, he will not acquire wisdom from his teacher. It reminds me of Kohut's, "the gleam in the mother's eye".
Intuitively, I get the explanation. But I am not able to translate "masbir panim" in order to get a precise p'shat in Rashi's explanation.
I have read Rishonim on Pirkey Avot 1, 16, (נוהג משא ומתן באמונה), "sever" (סבר) panim yafot and also Gemarot. "Sever" is apparently a "opened and directed face".
See Sefer He'aruch witch quotes a lot of chazal.
Is that openness?