the reason the malach told Hagar not to flee: how can you leave Eretz Yisrael?!

1) Rashi interprets the angel's question to Hagar, וַיֹּאמַ֗ר הָגָ֞ר שִׁפְחַ֥ת שָׂרַ֛י אֵֽי־מִזֶּ֥ה בָ֖את וְאָ֣נָה תֵלֵ֑כִי (16:8), as a rhetorical device. The angel knew where Hagar had come from and where she was headed to, but wanted an opening to engage her in conversation. Abarbanel, however, reads the pasuk as a statement and not a question:

והנה המלאך אמר לה ראשונה הגר שפחת שרי אי מזה באת ואנה תלכי ר״ל איך לא יעלה על לבך מאין יצאת שהוא בית אברהם עשיר ונדיב לבב אוהב אותך ואנה תלכי במדבר השמם הזה התמצאי בו בית נכבד כבית אברהם הביטי וראי גבול מה שממנו נסוגות וגבול מה שאליו תלכי.

The malach was telling Hagar to think carefully about the fact that she was leaving the home of a rich, benevolent person who loves her to go wander in the desert. For what?  Will the grass really be greener elsewhere?

Seforno also reads the malach's words as a statement, and I think Seforno's reading fits nicelywith theme of our entire parsha, namely the importance of Eretz Yisrael.  Seforno writes that the malach stressed to Hagar that by fleeing she was not just running away from Avahram's home, but also from Eretz Yisrael:  

 והנך הולכת בחוצה לארץ אל מקום טמא ואנשי רשע. 

Such an appeal only makes sense if Hagar could understand the importance of Eretz Yisrael, the kedusha of Eretz Yisrael.  Perhaps it's not by accident that it is davka Hagar's descendants who are fighting us tooth and nail for Eretz Yisrael. 

2) In the last halacha in the last perek of Brachos in the Yerushalmi (67b), there is a sugya that reads as follows:

אַבְרָהָם אָבִינוּ עָשָׂה יֵצֶר הָרַע טוֹב דִּכְתִיב: וּמָצָאתָ אֶת לְבָבוֹ נֶאֱמָן לְפָנֶיךָ. אָמַר רִבִּי אָחָא וְהִפְסִיד אֶלָּא וְכָרוֹת עִמּוֹ הַבְּרִית.

It sounds like R' Acha is asking a kashe, but it's not at all clear what the kashe is or what the teirutz is. How can a person lose anything by overcoming their yetzer ha'ra? Isn't that something we should be striving for? The Pnei Moshe must have been struggling with this point.  In order to make sense of things he changes the girsa. Instead of וְהִפְסִיד, he says the word should be והפשיר. It's not a kashe but rather a statement:

והפשיר עמו וכרות עמו הברית וגו׳ – כצ״ל וכן הוא בסוטה היצה״ר עשה פשרה ושלום עמו ודרש וכרות עמו הברית אדלעיל ומצאת את לבבו וגו׳

Chida in his sefer Rosh David (my cousin-in-law R' Avraham Wagner quotes the mareh makom in his sefer Afar Yerushalayim on the Ylmi) on our parsha defends the original girsa and explains what bothered R' Acha. If you don't have a yetzer ha'ra that fights back, then וְהִפְסִיד, because you lose the reward of overcoming the obstacles, challenges, and difficulties that stand in the way of your avodas Hashem.  We may at times bemoan the fact that we have to struggle so hard, but it is that struggle gives value and meaning to what we achieve.

Chazal tell us (Kid 31a) דְּאָמַר רַבִּי חֲנִינָא: גָּדוֹל מְצֻוֶּוה וְעוֹשֶׂה מִמִּי שֶׁאֵינוֹ מְצֻוֶּוה וְעוֹשֶׂה. Even though one might think that doing something voluntarily is greater than obeying a command to do so, Tos explains נראה דהיינו טעמא דמי שמצווה ועושה עדיף לפי שדואג ומצטער יותר פן יעבור ממי שאין מצווה שיש לו פת בסלו שאם ירצה יניח. When you have to do something, when there is a command to do something, the yetzer ha'ra fights back and tries to stop you. When you do something voluntarily, the yetzer ha'ra doesn't get in the way because there is no penalty for just walking away if things get too tough.  When there is no pressure and no obstacles to success, the accomplishment is not as great, and the reward for success, in turn, is diminished.

The teirutz of the Yerushalmi is that Avraham didn't lose, because it is only as a *result* of his pushing to overcome difficulties and do a milah that Hashem rewarded him with that blessing of וְכָרוֹת עִמּוֹ הַבְּרִית. Turning the yetzer ha'ra to good was not a means to enable him to do the mitzvah without any obstacles, but rather was a reward for having overcome the obstacles and done the mitzvah.

(The Chida gets involved in this whole discussion to solve the following problem: some explain that while Avraham did all mitzvos even without a command from G-d, he did not do a milah until commanded because he wanted to do it as a מצווה ועושה and not as an ֶאֵינוֹ מְצֻוֶּוה. Other mitzvos he could do multiple times, but when it comes to milah, you only have one chance.  Asks Chida: if the advantage of being מצווה ועושה is that you have a yetzer ha'ra to fight against, as Tos explains, then what did Avraham gain?  He had eliminated his yetzer ha'ra? It must be, says Chida, that that transformation too place as a result of the milah, but not beforehand.  Ayen sham for other approaches he offers.)

3) A famous gemara in Brachos 10a

הָנְהוּ בִּרְיוֹנֵי דַּהֲווֹ בְּשִׁבָבוּתֵיהּ דְּרַבִּי מֵאִיר וַהֲווֹ קָא מְצַעֲרוּ לֵיהּ טוּבָא. הֲוָה קָא בָּעֵי רַבִּי מֵאִיר רַחֲמֵי עִלָּוַיְהוּ כִּי הֵיכִי דְּלֵימוּתוּ. אָמְרָה לֵיהּ בְּרוּרְיָא דְּבֵיתְהוּ: מַאי דַּעְתָּךְ — מִשּׁוּם דִּכְתִיב ״יִתַּמּוּ חַטָּאִים״, מִי כְּתִיב ״חוֹטְאִים״? ״חַטָּאִים״ כְּתִיב.

Beruria tells R' Meir to daven that sin חַטָּאִים, be abolished, but don't pray for the demise of sinners, חוֹטְאִים.

Is there really such a difference between these terms?  Sefas Emes asks: what about the pasuk in our parsha (13:3) ואנשי סדם רעים וחטאים לה' מאד? The word חטאים there refers to the people, not to their actions?  Take a look at the meforshim on the Ein Yaakov.

4) A bit of trivia: a din buried in hilchos brachos that is learned from our parsha. OC 46:4:

צריך לברך בכל יום שלא עשני גוי שלא עשני עבד שלא עשני אשה: הגה ואפי' גר יכול לברך כן

The M"B explains the Rama as follows:

יכול לברך - פי' שיאמר שעשני גר דמיקרי עשייה כדכתיב ואת הנפש אשר עשו בחרן. ויש חולקין בזה וטעמם דלא שייך לומר שעשני דהגיור לא היתה כ"א מצד בחירתו הטובה שבחר בדת האמת