Emphasis

In western cultures, in order to emphasize something, a person who is speaking raise their voice. In written text, an important passage is often emphasized by underlining it or by using a bold typeface.
In Hebrew culture however, the same meaning is either repeated in a slightly different way or contrasted through its opposite meaning.

Repetition

It seems that the Hebrews knew thousands of years ago what we are learning now: Repetition makes it easier for us to remember something. Repetition is what everyone uses to memorize any type of information. In Hebrew, it is used as an emphasis.

Examples

So God created man in his own image,
in the image of God he created him,
male and female he created them.
Gen. 1:27

In this next example, keep in mind that the word for spirit, in Hebrew, can also mean breath:

The Spirit of God has made me,
and the breath of the Almighty gives me life.
Job 33.4

Here, the the exact same Hebrew word was repeated, not only the meaning:

To you they cried and were rescued;
in you they trusted and were not put to shame.
Psalm 22:5

These repetitions occur as much in the Gospels, which again shows how deeply rooted this Hebrew mindset was even in the first century. In this case, the idea, i.e. the concept of influencing the surroundings, is repeated:

You are the salt of the earth.
You are the light of the world.
Mat. 7:13a&14a

Contrast

The contrast shows the importance of a certain statement through the opposite meaning. For instance, you will only notice that bread needs salt if you have tasted unsalted bread before.

Examples

The book of Proverbs is probably the one where this method of emphasis is most used:

Blessings are on the head of the righteous,
but the mouth of the wicked conceals violence.

Whoever walks in integrity walks securely,
but he who makes his ways crooked will be found out.
Prov. 10:6,9

Yeshua (Jesus) uses this method in his teachings as well:

[The kingdom of God] is like a grain of mustard seed, which, when sown on the ground, is the smallest of all the seeds on earth,
yet when it is sown it grows up and becomes larger than all the garden plants and puts out large branches, so that the birds of the air can make nests in its shade.
Mark 4:31-32