Galatians 4:9-11

9Now, however, since you have come to know [the true] God [through personal experience], or rather to be known by God, how is it that you are turning back again to the weak and worthless elemental principles [of religions and philosophies], to which you want to be enslaved all over again?

10[For example,] you observe [particular] days and months and seasons and years.

11I fear for you, that perhaps I have labored [to the point of exhaustion] over you in vain.