John Trapp on Esther 9:21

Verſe 21. To eſtabliſh this among them] ſcil. by a law, that they ſhould yearly on thoſe two dayes reſt, and repeat among themſelves that ſignal deliverance, propagating the remembrance of it to all poſterity. Mordecai well knew that eaten bread is ſoon forgotten, that deliverances are uſually but nine dayes wonderment, that it is eaſie and ordinary with people, to rob God and wrong themſelves by their unthankfulneſſe, which forfeiteth former mercies and foreſtalleth future, he therefore ſetleth it upon them, ſaith the text, ſtatuendo eis ut facerent, he exacteth it of them by vertue of his office.

That they ſhould keep the fourteenth day, and the fifteenth day] Both dayes, nam gaudet produci haec ſclennitus, as Auſtin ſaid of the feaſt of Pentecoſt, ſuch a ſolemnity ſhould be drawn out to the full length, as the ſilk-worm ſtretcheth forth her ſelf, before ſhe ſpinneth her fineſt thread. Jehoſaphat and his people ſhewed themſelves unſatisfyable in their praiſes, which they preſented again, and again, 2 Chron. 20.26, 27. And good Hezekiah, when he obſerved in his ſubjects ſuch a float of affections at the Paſſeover, and that they were in ſo good a frame, took counſel with them to keep other ſeven dayes, and they kept other ſeven dayes with gladneſſe, 2 Chron. 30.21, 22, 23. See with what a flood of words holy David poureth forth his ſoul in prayer, Pſal. 145.1. to 8. as if therewith he would even fill up the diſtance between God and himſelf. Sometimes he ſeemeth to forget himſelf in point of praiſing God; for he will, like a bird, having got a note, record it over and over, as Pſal. 136. And in the laſt Pſalme, there are but ſix verſes: yet twelve Hallelujahs. He concludeth, Let every thing that hath breath, or, Let every breath praiſe the Lord, let it be as the ſmoke of the Tabernacle, when peace-offerings, were offered, Tam Dei meminiſſe opus eſt quàm reſpirare, ſaith Chryſoſtom, we have as much need to remember God, as to take breath.