'Mysteries' in the Bible

Thus let a person consider us as servants of Christ and stewards of God's mysteries.

And if I have [the gift of] prophecy and I know all mysteries and all knowledge, and if I have all faith so that [I can] remove mountains, but do not have love, I am nothing.

For the one who speaks in a tongue does not speak to people but to God, because no one understands, but by the Spirit he speaks mysteries.