The passage "על כן בשכר זאת קל חי חלקנו צורנו צוה להציל ידידות שארנו משחת" is part of one of the blessings recited at a b'ris mila. Pische S'shuva (Yore Dea 265:4) cites a difference of opinion as to whether the word "צִוָּה / tziva / commanded" or "צַוֵּה / tzave / command" appears in it, and concludes that either is okay. (The commentaries he quotes discuss why one word might be better than the other.) In practice, which communities recite each?
 That is, "therefore, in this merit, the living God… commanded to save…".
 That is, "therefore, in this merit, O living God… command to save…".