The Purpose of the Makkos Was to Establish Emunah

"ויאמר ה' אל משה נטה את ידך על השמים ויהי ברד בכל ארץ מצרים" (כב ט)

אל משה נטה– the acronym of these words is amen, to allude that the purpose of the makkos in Mitzrayim was to establish emunah in the hearts of Am Yisrael, as it says in the closing of the miracles (Shemos 14:31): "Vaya’aminu b’Hashem ubeMoshe avdo." (Niflaos MiTorasecha, Amen)