Good Eye

וְהָיָ֣ה הַֽנַּעֲרָ֗ אֲשֶׁ֨ר אֹמַ֤ר אֵלֶ֙יהָ֙ הַטִּי־נָ֤א כַדֵּךְ֙ וְאֶשְׁתֶּ֔ה וְאָמְרָ֣ה שְׁתֵ֔ה וְגַם־גְּמַלֶּ֖יךָ אַשְׁקֶ֑ה אֹתָ֤הּ הֹכַ֙חְתָּ֙ לְעַבְדְּךָ֣ לְיִצְחָ֔ק וּבָ֣הּ אֵדַ֔ע כִּי־עָשִׂ֥יתָ חֶ֖סֶד עִם־אֲדֹנִֽי.  The siman for the right one is not only does she give Eliezer to drink as was requested of her but she adds that she will give the camels water.  The Kli Yakar cleverly notes that the word גמל is close to the words גמילות חסד as a hint that this proves she is a real chesed oriented individual.  Why does she have to add beyond the request of Eliezer to prove she is a baalat chesed?  The Kli Yakar says because doing chesed even with a being that's not her species, out of her orbit, proves she is a real baalat chesed and not just looking out for her own.  Some say that when one helps out someone who is in a state of need that may just be because one feels sorry for the other person.  It is a real chesed, a giving just to give, when one does chesed even if the other person doesn't need help.  Eliezer was a weary traveler and asked for water so Rivka may just feel bad for him and give him to drink.  It is only when she goes beyond that which the other person needs that proves she is helping just in order to do chesed.  I would just add that although she was not bound by a request of Eliezer, a young girl may feel intimated to grant the request of an elderly man such as Eliezer.  However, to add to his request proves she is a baalat chesed. 

The Kli Yakar adds רז״ל אמרו (תענית כד.) כל כלה שעיניה יפות כל גופה אין צריך בדיקה. וזה דבר שהחוש מכחיש כי כמה מכוערות בעולם שעיניהן יפות. ועוד קשה מה ראו חז״ל על ככה ליתן עצה לבדוק אחר יופי חיצוני זה והלא שקר החן והבל היופי, אלא ודאי שנתנו עצה לבדוק אחר מעשיה וזאת העצה היעוצה שיבדוק אם היא בעלת עין יפה וגומלת חסדים, כי אם עיניה יפות בבריות, אז היא בלי ספק שלימה בכל המדות, ולמדו רז״ל מן אליעזר שלא בדק את רבקה כי אם במדה זו כי מדה זו בנין אב על כל המדות.

I saw in the sefer Bishviley Haparsha that this may also be hinted to by the terminology the Torah uses.  Eliezer meets Rivka at a spring of water, normally called a באר which is the word used in pessukim 11,20.  However, many more times during the episode it is called עין המים.  Why is this terminology used?  He suggests it is hinting to this idea, to look at the eye.  To see is she has a good eye (not in baseball,) to be a giving person (see more about the relationship here.) 

[It is still צ"ע why it switches from באר to עין and back and as pointed out in the linked article, Hagar is approached by the malach at the עין המים and she calls it באר לחי רואי, why the switch?  (See the Malbim by the episode of Hagar here, but that doesn't seem to help us in our parsha.)   See also here a connection between Yitzchak and באר לחי רואי.]

We see from the hanhaga in this episode that was most important to check into the prospective shidduch was if the girl is a baalat chesed.