This is the qualification for anyone who sees the need for correction. If you are not spiritual then you have no place or right to be telling another how they ought to behave. And of course it is for all of us to be spiritual, though sadly this is often not the case. And such a person will be led by the Holy Spirit. Secondly, the correction is to be given in the spirit of meekness.
Gentleness is the characteristic of true spirituality.
Now a spirit of meekness does not mean an easy-going tolerance of evil. We are to always be intolerant of any evil in our midst. Our Lord Jesus here becomes our perfect example. He also possessed a spirit of meekness. He did not condemn her but simply said, go, and sin no more.