Exodus 12:6
4 If any household is too small for a lamb, the man and his next-door neighbor are to take a lamb according to the number of people—you will make your count for the lamb according to how much each one can eat. 5 Your lamb must be perfect, a male, one year old; you may take it from the sheep or from the goats. 6 You must care for it until the fourteenth day of this month, and then the whole community of Israel will kill it around sundown. 7 They will take some of the blood and put it on the two side posts and top of the doorframe of the houses where they will eat it. 8 They will eat the meat the same night; they will eat it roasted over the fire with bread made without yeast and with bitter herbs.
Esther 3:12
10 So the king removed his signet ring from his hand and gave it to Haman the son of Hammedatha, the Agagite, who was hostile toward the Jews. 11 The king replied to Haman, “Keep your money, and do with those people whatever you wish.” 12 So the royal scribes were summoned in the first month, on the thirteenth day of the month. Everything Haman commanded was written to the king’s satraps and governors who were in every province and to the officials of every people, province by province according to its script and people by people according to their language. In the name of King Ahasuerus it was written and sealed with the king’s signet ring. 13 Letters were sent by the runners to all the king’s provinces stating that they should destroy, kill, and annihilate all the Jews, from youth to elderly, both women and children, on a particular day, namely the thirteenth day of the twelfth month (that is, the month of Adar), and to loot and plunder their possessions.
Notes and References
"... The dating by months and days used since the exilic period (compare Ezekiel 24:2 “name [= date] of the day”) consistently employs yom alongside the cardinal number (about 40x, Aramaic Ezra 6:15), although yom is often omitted (e.g., Haggai 2:1, 10; Esther 9:17 alongside Hag 1:1, 15; 2:18; Esther 9:17a with yom; regularly in the date of the reception of revelation in Ezekiel 1:1–40:1). The dates refer mostly to festival days (Exodus 12:6, 18, etc., in Exodus - Numbers; Joshua 5:10; 1 Kings 12:32; Ezekiel 45:21, 25; Esther 3:12; 9:1, 15, 17, 19, 21; Ezra 3:6; Nehemiah 8:2; 9:1; 2 Chronicles 7:10; 29:17; consequently, the 14th and 15th days of the month are named most often), less often to prophetic reception of revelation (Haggai 1:1, 15; 2:18; Zechariah 1:7; Daniel 10:4) or to other experiences (Genesis 7:11; 8:4, 14; Exodus 16:1 in the P narrative) ..."
Jenni, Ernst, and Claus Westermann Theological Lexicon of the Old Testament (pp. 690-691) Hendrickson Publishers, 1997