There is a story about someone who wrote a periush on tefilla and wanted a haskama from the GRA. The GRA looked through it and found a reason why adon olam was put before shacris davening.The reason which was given was from what Rabbi Shimon Bar Yochai said since the world was created no one called Hashem adon until Avraham Aveinu.Avraham also was the one who instituted Shachris, it is then befitting to place adon olam before the tefillah that was set up by the person who called Hashem adon first. After the GRA saw this he was b’simcha and said this sefer is worthy of printing for this perish alone.(kemotzei shalal Rav)
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