EG, it actually says a 'firm covenant with many' not confirm. Shalom
the word used:
1504 גָּבַר (gā∙ḇǎr): v.; ≡ Str 1396, 1399; TWOT 310a—1. LN 88.206–88.222 (hitp) show oneself arrogant, vaunt oneself, be overbearing, i.e., have attitudes and actions showing hubris and pride (Job 15:25; 36:9+); 2. LN 34.22–34.30 (hif)
confirm, i.e., to establish a relationship with a person or group (Da 9:27+); 3. LN 16 (qal) rise, flood, i.e., have a mass swell or rise higher (Ge 7:18, 19, 20, 24+), note: as a non-linear movement of water; 4. LN 21.1–21.5 (qal) overwhelmed, inundated, formally, flooded over, i.e., be in a state of danger, as a figurative extension of being flooded over by a mass of water (Ps 65:4[EB 3]+); 5. LN 78.28–78.39 (qal) be greater, be more, i.e., have a degree greater that is normal, compared to another point on a scale (Ge 49:26; 2Sa 1:23; Job 21:7; Ps 103:11; 117:2+); (piel) be greater, be more, (Ecc 10:10+); 6. LN 76 (qal) be strong, i.e., be in a state of strength and ability (1Ch 5:2+); (piel) strengthen, i.e., make an object mighty and forceful (Zec 10:6, 12+), note: in context, apparently military strength, see also domain LN 74; 7. LN 39.52–39.61 (qal) win over, have a victory over (Ex 17:11; 1Sa 2:9; 2Sa 11:23+); (hif) triumph over, i.e., make a conquest and so a victory over an enemy (Isa 42:13+); 8. LN 33.387–33.403 unit: (hif) לָשֹׁון גָּבַר (lā∙šôn gā∙ḇǎr) slander, formally, be strong of tongue, i.e., speak in attacking ways such as slander and insult (Ps 12:5[EB 4]+)
Swanson, J. (1997). Dictionary of Biblical Languages with Semantic Domains : Hebrew (Old Testament) (electronic ed.). Oak Harbor: Logos Research Systems, Inc.
I see nothing there says says "firm" is a possible translation.
Confirm in this sense means to establish a relationship with someone, Which means it is new. you don't establish something that is already in place.