One bird in the hand is worth two flying (or on the roof), [281], [316], [343] (See A bird)
One bite brings another, [351]
One blind man leads another into the ditch, [60]
One briar does not make a hedge, [130]
One can speak and seven can sing, [142]
One candle for St. Michael, and another for his devil, [61]
One cannot be and have been, [42]
One cannot be at the oven and the mill at the same time (One cannot be in two places at once), [42]
One cannot blow and swallow at the same time, [258]
One cannot drink and whistle at the same time, [114] (See No one)