what happened on erev rosh chodesh Sivan

The talmidim of Chasam Sofer bring down that the CS fasted on erev rosh chodesh Sivan and dedicated the day to teshuvah.  Chazal tell us that when Klal Yisrael left Refidim they did teshuvah and when they arrived at Sinai the next day on rosh chodesh SIvan they did teshuvah  (see post here).  Rashi comments (Shmos 19:2)

ויסעו מרפידים – מה ת״ל? לחזור ולפרש מהיכן נסעו, והלא כבר כתוב שברפידים היו חונים (שמות י״ז:א׳), בידוע שמשם נסעו. אלא להקיש נסיעתן מרפידים לביאתן למדבר סיני, מה ביאתן למדבר סיני בתשובה, אף נסיעתן מרפידים בתשובה.

Apparently the day is a special day and an eis ratzon.  There is a special tefilah composed by the SHL'H to recite on this day for the sake of one's children.  Since erev rosh chodesh this year falls out on shabbos, the question is raised as to whether one can recite this bakasha on shabbos, as normally we refrain from personal bakashos on shabbos.  I saw R' Chaim Kamievsky is quoted both ways, so either he gave different answers at different times, changed his mind, or someone got it wrong.  On the one hand, this is a once a year opportunity, and one is asking for tzorchei Shamayim, for one's children to grow in Torah and yiras Shamayim, not for mundane needs.  On the other hand, a bakasha is still a bakashah, and you can always say a tefilah for your kids before Shabbos or after Shabbos, or every day of the year for that matter. 

In general, poskim debate how far to take this rule of no bakashos, as we have many tefilos that do not seem consistent with it.  For example (since it's Shabbos mevorchim), the Aruch haShulchan (OC 417:9) has a problem with saying the last paragraph of birchas ha'chodesh:

 

אך מה שאומרים ה"יהי רצון" מקודם – תמיהני היאך מותר להתפלל בשבת תפילה חדשה, מה שאינה בטופס ברכות, אלא תפילה בפני עצמה? ומבקשים על פרנסה ושארי צרכים, ואיך מותר בשבת?

 

The GR"A would not say the haRachaman section of bentching on Shabbos because it is bakashos.  Others are more lenient when it comes to these things.

 

When we read וַיִּסְע֣וּ מֵרְפִידִ֗ים וַיָּבֹ֙אוּ֙ מִדְבַּ֣ר סִינַ֔י וַֽיַּחֲנ֖וּ בַּמִּדְבָּ֑ר וַיִּֽחַן־שָׁ֥ם יִשְׂרָאֵ֖ל נֶ֥גֶד הָהָֽר we have to keep in mind what happened in Refidim: (Shmos 17:8):

 

וַיָּבֹ֖א עֲמָלֵ֑ק וַיִּלָּ֥חֶם עִם־יִשְׂרָאֵ֖ל בִּרְפִידִֽם

וַיֹּ֨אמֶר מֹשֶׁ֤ה אֶל־יְהוֹשֻׁ֙עַ֙ בְּחַר־לָ֣נוּ אֲנָשִׁ֔ים וְצֵ֖א הִלָּחֵ֣ם בַּעֲמָלֵ֑ק מָחָ֗ר אָנֹכִ֤י נִצָּב֙ עַל־רֹ֣אשׁ הַגִּבְעָ֔ה וּמַטֵּ֥ה הָאֱלֹהִ֖ים בְּיָדִֽי

 

Bn"Y arrived in Sinai on the heels of the battle against Amalek.  If they arrived on rosh chodesh, it means that battle took place on erev rosh chodesh, when the moon is invisible.  Klal Yisrael is compared to the moon.  When the moon is renewed, it represents the renewal and rejuvenation of Klal Yisrael.  When the moon wanes, it is a time of din.  Rosh haShana, the yearly Yom haDin, is "b'keseh l'yom chageinu," when the moon is hidden.  On erev rosh chodesh, the old moon is completely invisible as we wait for the new moon to appear.  This is why Amalek chose this time to attack. 

 

Moshe chose Yehoshua to lead the fight because, "Pnei Moshe k’pnei chamah u’pnei Yehoshua k’pnei levana," (B"B 75) Yehoshua is compared to the moon.  When Moshe passed away, Klal Yisrael didn't fade away and collapse.  The waning of the period of Moshe's life was followed by the waxing of the conquest of Eretz Yisrael.  A period of darkness when the old moon fades away is just a preparation for a period of increased light.  (Panim Yafos end of Beshalach)