Do not accept anything as the truth if it lacks love. And do not accept anything as love which lacks truth.Attr. St. Teresa Benedicta of the Cross (Edith Stein)
The saying is found in Pope St. John Paul II’s homily for her canonization. The exact passage, with punctuation and italics as in the original, looks like this:
St Teresa Benedicta of the Cross was able to understand that the love of Christ and human freedom are intertwined, because love and truth have an intrinsic relationship. The quest for truth and its expression in love did not seem at odds to her; on the contrary she realized that they call for one another.
In our time, truth is often mistaken for the opinion of the majority. In addition, there is a widespread belief that one should use the truth even against love or vice versa. But truth and love need each other. St Teresa Benedicta is a witness to this. The “martyr for love”, who gave her life for her friends, let no one surpass her in love. At the same time, with her whole being she sought the truth, of which she wrote: “No spiritual work comes into the world without great suffering. It always challenges the whole person”.
St Teresa Benedicta of the Cross says to us all: Do not accept anything as the truth if it lacks love. And do not accept anything as love which lacks truth! One without the other becomes a destructive lie.
Throughout the homily, when the Holy Father was quoting St. TBotC’s words, they are placed in quotation marks (see the end of the second paragraph above). The alleged saying is not in quotation marks–it’s italicized, as are other points that Pope St. JP II wanted to emphasize.
If there’s any doubt about it, a look at the context makes it clear that the quoted phrase is JP II’s summary of (a part of) St. Theresa Benedicta of the Cross’s message; it’s not something that she herself said, in so many words. Someone saw “says to us all” and misread it (in my opinion, but backed by evidence) as attributing the saying to her.
Verdict: Fauxtation; actually a saying of Pope St. John Paul II.