3 “Then the disciples looked one on another, doubting of whom He spoke.” For while they were imbued with a reverential love to their Master, they were none the less affected by human infirmity in their feelings towards each other. Each one's own conscience was known to himself; but as he was ignorant of his neighbor's, each one's self-assurance was such that each was uncertain of all the others, and all the others were uncertain of that one.
Source: Tractates on the Gospel of John (New Advent)