Wiktionary
vb. 1 (context intransitive English) to retain one's faith 2 (context transitive English)to continue to have confidence in someone or something, and to support them or it
Usage examples of "keep faith".
The first method is when witches meet together in the conclave on a set day, and the devil appears to them in the assumed body of a man, and urges them to keep faith with him, promising them worldly prosperity and length of life.
We also have to be sure that they will believe in us, and keep faith with us, even after they've heard Sartol's accusations.
It is thus evident, that force and necessity, not deeds and obligations, induce princes to keep faith.
Until then, I must keep faith with my duty to protect the Motherland.
Either Mason cannot admit there's a Class problem here, or, even this deeply compromised, he may yet somehow keep Faith that in the Service of the Heavens, dramatic Elevations of Earthly Position are to be expected of these Times, this Reign of Reason, by any reasonable man.
Whatever the duke might promise the Swede or the up-timers or Duke Ernst in return for concessions, there was, in fact, no obligation to keep faith with heretics.
Does that mean I must keep faith with them even if they do me villainy?