Permanence of Yirah

וַתִּירֶ֤אןָ הַֽמְיַלְּדֹת֙ אֶת האלקים וְלֹ֣א עָשׂ֔וּ כַּֽאֲשֶׁ֛ר דִּבֶּ֥ר אֲלֵיהֶ֖ן מֶ֣לֶךְ מִצְרָ֑יִם וַתְּחַיֶּ֖יןָ אֶת־הַיְלָדִֽים.  A few pessukim later it says וַיְהִ֕י כִּי־יָֽרְא֥וּ הַֽמְיַלְּדֹ֖ת אֶת האלקים וַיַּ֥עַשׂ לָהֶ֖ם בָּתִּֽים:  Why does the Torah need to repeat that they feared Hashem?  Why does the Torah put the emphasis that the motivation of their actions stemmed from a fear of Hashem and not due to their car for the babies?  What is the middah keneged middah in their reward which Rashi tells us is receiving kehunah and malchus?  

We see that the actions of the midwives were motivated by their fear of heaven.  In the situation where they were in with a threat of the king over their head, it was not their feelings of love that would be enough to put their life in danger.  It is only due to their fear of heaven, of violating the commandments of Hashem, that forced them to do the right thing.  

The Shem MiShmuel (5674) says a house is something of permanence as the Gemarah beginning of Sukkah says.  Yiras Shamayim is the house, the אוצר (see Shabbas 31a,) which keeps everything else going.  Since the midwifes exhibited yirah, an אוצר which gives permanence to all of one's avodas Hashem, in reward they receive houses of permanence in form of the linage of kehuna and malchus. 

What does it mean that yiras shamayim gives permanence?  Yirah is the fall back that that spurns one's avodah in times of difficulty.  Like the midwives that had to make a difficult choice and were guided by their yiras shamayim, so tooone's avodah remains constant only if it is spurred on by yirah.  Feelings of ahavah have peaks and valleys, but yirah is a fallback that allows avodah's Hashem to be a constant.