Oxidation and reduction go together
Electrons lost by one substance are gained by another, so oxidation and reduction always happen at the same time.
A worked example
Drop zinc metal into copper(II) sulfate and each zinc atom loses two electrons and is oxidised, while each copper ion gains them and is reduced.
The mistake people actually make
A spontaneous redox reaction runs on its own, which is how a battery works; a non-spontaneous one has to be driven by an outside supply, as in electrolysis.