English. Such a simplified language....it is much easier to define such a belief in other languages. Even if I try to translate the meaning, it would still sound odd in this language, but it is the difference between merely believing in something like the sky appears blue and believing into something like believing into the existence of God. One can believe in God in a passive form, but one can have an existential active belief in God.
But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus, His Son, purifies us from all sin.