In parshah Shemos, we learn that the Jewish midwives Shifrah and Puah defy Pharoah's instructions to kill all male babies, despite Pharoah's threat to execute them if they disobey his order. Midrash explains that Shifrah and Puah were in fact Yocheved and Miriam, respectively, and their decision to save the male babies was due to their fear of Hashem / heaven being greater than their fear of a mere mortal.
It was their profound Yirat Shemayim that provoked them to not only attempt to save all Jewish babies during delivery, but to spur them to follow every available path to ensure success in their decision. To that end, the pair davened to Hashem to not only spare the babies, but to have those previously destined for weakness or defects be born 100% healthy, as well as to have no woman die in childbirth or otherwise be harmed. In this way, they would be above suspicion and nobody would suspect them of attempting to carry out Pharoah's orders.
Yet they did not stop there. In keeping with the notion that "Hashem helps those who help themselves", their love of the klal caused them to take practical measures, such as gathering food from rich homes to distribute it to poor homes, so that all children could be fed. In this way they further helped the new mothers sustain newborns.
For her selfless efforts born of her ahavas yisroel and Yirat Shemayim, at the threat of loss of her own life, Hashem repaid Yocheved middah-kenneged-middah. Yocheved merited to become the mother of all future leviim (Moshe) and kohanim (Aharon)- the groups that similarly serve the nation at the expense of their own comfort, and whose members rely upon the good-will of the nation to survive. It is this trait that enables kohanim to bless the klal with a heart overwhelming with love and otherwise act as a crucible for Hashem's blessing of the nation. Just as through Yocheved the nation was blessed, through her descendants, the nation continues to be blessed.
Who else but the woman who personified an utmost commitment to Hashem and his people, a commitment based on awe and love of Hashem, could become the matriarch of the tribe that embodies selfless devotion to Hashem and his people?