Short Latin prayer?

On Sunday afternoon I went to Vespers and Benediction at the Cathedral. After the Divine Praises the archdiocesan Prayer for Vocations and the Prayer for Reverence for Life were prayed but then they prayed a really short (one line) Latin prayer three times over in reparation for abortion. I can't remember the Latin but I think a rough translation (as far as I can remember) was something along the lines of "Lord have mercy on [forgive? I can't remember exactly.] your people, do not remain angry with us forever." I thought it was a very appropriate prayer for the intention of praying in reparation for the horrors of abortion and it brought tears to my eyes since I had only a few hours earlier been speaking with someone about the abortion rates in Canada (close to 1 in 4 pregnancies end in abortion). Anyways, this is maybe a shot in the dark, but does someone know the prayer I'm talking about? What's it called? How does it go in Latin? In English? Thanks.

Update - prayer has been found:

Parce domine, parce populo tuo, ne in aeternum irascaris nobis.

"Spare your people, Lord; be not angry with us forever."