Deuteronomy 20:3
1 When you go to war against your enemies and see chariotry and troops who outnumber you, do not be afraid of them, for the Lord your God, who brought you up out of the land of Egypt, is with you. 2 As you move forward for battle, the priest will approach and say to the soldiers, 3 “Listen, Israel! Today you are moving forward to do battle with your enemies. Do not be fainthearted. Do not fear and tremble or be terrified because of them, 4 for the Lord your God goes with you to fight on your behalf against your enemies to give you victory.”
1 Maccabees 4:8
6 At daybreak Judas appeared in the plain with three thousand men, but they did not have armor and swords such as they desired. 7 And they saw the camp of the Gentiles, strong and fortified, with cavalry all around it; and these men were trained in war. 8 But Judas said to those who were with him, "Do not fear their numbers or be afraid when they charge. 9 Remember how our ancestors were saved at the Red Sea, when Pharaoh with his forces pursued them.
Notes and References
"... The second instance of this term comes at 1 Maccabees 4:8, which again has Judas speaking to his army before a battle with an opposing force made up of Syrians, Philistines (in an archaism repeated frequently in 1 Maccabees), and Seleucid soldiers. In this situation he commands his soldiers, “do not fear their numbers or be afraid of their charge.” Here again, we run into trouble with the Greek terms, but also have a connection to Deuteronomy 1:29 and 20:3. The speech by the priest Judas before his troops incites courage in them by reminding them of divine aid and recalls Deuteronomy 20:3. The recollection of divine aid of the ancestors while commanding Israel not to be afraid has some similarities with Yahweh’s instructions to Israel at Deuteronomy 1:29. In each case the context of war with the inhabitants of the land is in place. This suggests that the use of the term in 1 Maccabees is inspired by the Deuteronomic corpus ..."
Borchardt, Francis "The Deuteronomic Legacy of 1 Maccabees" in Weissenberg, Hanne von, et al. (eds.) Changes in Scripture: Rewriting and Interpreting Authoritative Traditions in the Second Temple Period (pp. 297-319) De Gruyter, 2011