“It behoved that there should be sin; but all shall be well, and all shall be well, and all manner of thing shall be well.”

The Thirteenth Revelation, Chapter 31
Context: And thus our good Lord answered to all the questions and doubts that I might make, saying full comfortably: I may make all thing well, I can make all thing well, I will make all thing well, and I shall make all thing well; and thou shalt see thyself that all manner of thing shall be well.

The Thirteenth Revelation, Chapter 32

Julian of Norwich (1983)

The Thirteenth Revelation, Chapter 32
Context: Our Faith is grounded in God’s word, and it belongeth to our Faith that we believe that God’s word shall be saved in all things; and one point of our Faith is that many creatures shall be condemned: as angels that fell out of Heaven for pride, which be now fiends; and man in earth that dieth out of the Faith of Holy Church: that is to say, they that be heathen men; and also man that hath received christendom and liveth unchristian life and so dieth out of charity: all these shall be condemned to hell without end, as Holy Church teacheth me to believe. And all this standing, methought it was impossible that all manner of things should be well, as our Lord shewed in the same time.
And as to this I had no other answer in Shewing of our Lord God but this: That which is impossible to thee is not impossible to me: I shall save my word in all things and I shall make all things well. Thus I was taught, by the grace of God, that I should steadfastly hold me in the Faith as I had aforehand understood, therewith that I should firmly believe that all things shall be well, as our Lord shewed in the same time.
For this is the Great Deed that our Lord shall do, in which Deed He shall save His word and He shall make all well that is not well. How it shall be done there is no creature beneath Christ that knoweth it, nor shall know it till it is done; according to the understanding that I took of our Lord’s meaning in this time.

The Thirteenth Revelation, Chapter 34
Context: He is the Ground, He is the Substance, He is the Teaching, He is the Teacher, He is the End, He is the Meed for which every kind soul travaileth.
And this is known, and shall be known to every soul to which the Holy Ghost declareth it. And I hope truly that all those that seek this, He shall speed: for they seek God.
All this that I have now told, and more that I shall tell after, is comforting against sin. For in the Third Shewing when I saw that God doeth all that is done, I saw no sin: and then I saw that all is well. But when God shewed me for sin, then said He: All SHALL be well.

The Thirteenth Revelation, Chapter 32
Context: Our Faith is grounded in God’s word, and it belongeth to our Faith that we believe that God’s word shall be saved in all things; and one point of our Faith is that many creatures shall be condemned: as angels that fell out of Heaven for pride, which be now fiends; and man in earth that dieth out of the Faith of Holy Church: that is to say, they that be heathen men; and also man that hath received christendom and liveth unchristian life and so dieth out of charity: all these shall be condemned to hell without end, as Holy Church teacheth me to believe. And all this standing, methought it was impossible that all manner of things should be well, as our Lord shewed in the same time.
And as to this I had no other answer in Shewing of our Lord God but this: That which is impossible to thee is not impossible to me: I shall save my word in all things and I shall make all things well. Thus I was taught, by the grace of God, that I should steadfastly hold me in the Faith as I had aforehand understood, therewith that I should firmly believe that all things shall be well, as our Lord shewed in the same time.
For this is the Great Deed that our Lord shall do, in which Deed He shall save His word and He shall make all well that is not well. How it shall be done there is no creature beneath Christ that knoweth it, nor shall know it till it is done; according to the understanding that I took of our Lord’s meaning in this time.

The Political Report of the Central Committee, The Fifteenth Congress of the C.P.S.U.(B.) (7 December 1927) http://marx2mao.com/Stalin/FC27.html#s5iii
Stalin's speeches, writings and authorised interviews

circulated since early 2015, debunked by Snopes in June 2016 https://www.snopes.com/fact-check/warren-disarm-them-ourselves/. Resembles the Stalin-attributed "If the opposition disarms, well and good. If it refuses to disarm, we shall disarm it ourselves."
Misattributed

Harmonices Mundi (1618)