The answer
Yes, the Bible says that there is "one baptism", but please let us read a bit more of the verse, which tells us that there is "one faith" and "one baptism".
For wherever one faith exists, one baptism is found too.
Therefore we don't re-baptise a person who has been baptised in a church which shares our Orthodox faith.
Also, baptism must be performed by a properly qualified priest who has full priestly authority to carry out the holy sacrament
of baptism, and who believes totally in the effective action of this sacrament.
For example, the churches which do not believe in the sacrament of the priesthood and which do not have priests and do not believe that baptism is a sacrament, do not share our belief in the effectiveness of baptism, so we can't really accept their baptism.
The same applies to churches which believe in the sacrament of baptism and its effectiveness and in the sacrament of the priesthood, but are closed to us according to anathemas set by the Fathers.
These anathemas must be removed first, then their church sacraments would be acceptable to us.
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Thrice-Blessed Pope Shenouda III of Blessed Memory