Goodbye!
is a very much used expression, although it is being taken over by See ya and Cheerio or shortened to bye and lengthened again to by-ee!  Goodbye itself is a shortened form.  It is really a blessing and means God be with ye!
(Ye is the plural of thee as you is the plural of thou.  Unfortunately previous generations became sloppy in their speech rendering it necessary for us to say things like “Would you both like to…”  Previously both would have been implied by the use of you.)

A godsend is an unexpected blessing.  If someone turns up at just the right moment to help in a crisis or a much needed gift arrives it could be described as a godsendSent by God.

God moves in a mysterious way is the first line of a hymn which continues
His wonders to perform.  Although God is always true to himself, his actions are not predictable.  Believers agree that He has our best interests at heart, but often surprises us.

The answer to a maiden’s prayer is a saying.  The person who has received a blessing may not be a young girl.

Polish your halo!
In Christian art Jesus, saints and angels have often been depicted with an aura of light around the head, known as a halo.  If someone boasts that they have done a good deed, they might be cut down to size by this remark.

A blessing in disguise is perhaps a disappointment which allows something better to happen later.

A mixed blessing is something which brings problems as well as advantages.

A stepmother’s blessing is a name for a loose piece of skin at the edge of a fingernail – a hangnail.

Fools rush in where angels fear to tread is a proverb about intervening in a situation where people might be upset.

In the lap of the gods is beyond human control.

Preaching to the converted is an expression, which has left church buildings and entered everyday speech.  Someone who is trying to convince others of the truth of a particular point of view may find that they are already of the same opinion.
(Not going to church, because you already believe the Gospel is not a valid excuse.  Sermons should also include teaching about growing in faith.)

A peace offering is an expression from the Old Testament.  Nowadays it is mainly used if someone takes a gift to patch up a quarrel.

A wing and a prayer appears under Necessity in the Oxford Dictionary of Phrase, Saying and Quotation.  It is explained as

reliance on hope or the slightest chance in a desperate situation.

Flying in the face of Providence is going against God, who is the creator and sustainer.

Flying in the face of nature is a similar idea.

A guiding star may be a real star, as in the case of the wise men from the East, or a mentor or role-model.

To the pure all things are pure.
An innocent mind does not suspect others of evil intentions or notice innuendo.

Man proposes; God disposes.  This proverb is filed under Fate in the reference book I mentioned above.  Belief in a Sovereign God and belief in Fate are two completely different things.  However our plans come to nothing if they are not part of God’s plan.

The grand scheme of things is a sort of overview.  I suggest there is an underlying belief in God behind this phrase.

There are plenty of religious jokes.  One of my favourites is

Where was Moses when the light went out?

In the dark!

Oh ye of little faith is a quotation from Matthew 6:30It is often said when someone is sceptical about whether something will work.