I've been hearing the phrase "This is not being meikil1 on Shabbos, this is being machmir2 on pikuach nefesh3" for a long time. I've heard it quoted from R' Chaim, from the Gra, and from various and sundry other sources.
It has also been, in my experience, applied to eating on Yom Kippur and other instances of pikuach nefesh, but I've always understood that the original quote was said about Shabbos.
Who was the originator of this line? Can I find it anywhere, "inside"?
3 the obligation to preserve one's life, which overrides Shabbos and most other mitzvos