1 Enoch 91:4
3 And he spoke to all the children of righteousness and said: 'Listen, sons of Enoch, to all the words of your father, and pay close attention to the sound of my voice; for I urge you and say to you, beloved: Love integrity and walk in its ways. 4 And do not approach integrity with a double heart, and do not associate with those who have a double heart, but walk in righteousness, my sons. It will guide you on good paths, and righteousness will be your companion. 5 For I know that violence must increase on the earth, and a great punishment will be executed on the earth, and all wickedness will come to an end: yes, it will be completely eradicated from its roots, and its entire structure will be destroyed.
Didache 4:4
2 Seek the company of holy people every day so you may find comfort in their words. 3 Don't seek division but reconcile those in conflict. Make fair judgments; don't show favoritism when correcting wrongs. 4 Don't be double-minded about whether something should be or not. 5 Don't be someone who is eager to receive but reluctant to give. 6 Give a portion of what you've earned with your hands as a ransom for your sins.
Notes and References
"... While the second instance, which brands “those of double heart” as a group, does not allow for ambiguity that conceives of them doing good as well as bad, the first occurrence holds open the possibility that anyone, perhaps even the righteous, might be subject to the “double heart”, and so warns them away. This point cannot, in the end, be pressed too far. The remaining emphasis on “two ways” throughout chapters 91–105 distinguishes the righteous and sinners or oppressors as social groups to such a degree that it is more likely that the righteous are simply being warned away from getting into a state of dividedness (i.e. sinfulness) to begin with ... A similar use of the motif of “double-mindedness” occurs within the “two ways” instruction in Didache 1:1–6:3; see especially 2:4 and 4:4 ..."
Stuckenbruck, Loren T. 1 Enoch 91-108 (p. 167) De Gruyter, 2007