John Gill Commentary Mark 14:69

"And the maid saw him, and began again to say to them that stood by, This is [one] of them." — Mark 14:69 (ASV)

And a maid saw him again
Either the same maid, so the Syriac and Persic versions read, "that maid": that selfsame maid, as before, or another, as in (Matthew 26:71) , and so the Arabic version reads it here; but the Ethiopic as before "a daughter": that is, of the high priest:

and began to say to them that stood by ;
the fire, along with Peter, warming themselves:

this is one of them ;
this man is one of the disciples and followers of Jesus of Nazareth; he is of that sect, he certainly belongs to them, and is come here only as a spy.