Have children

Contraceptives or not
Having children is the fundamental way of sustaining humanity.
Contraceptives prevent reproduction. Is that allowed?
What answers can we get from the Holy Books in connection with this?

Blessing
The list of blessings includes the birth of children.
The curses mention remaining childless.
From this, the conclusion must be drawn unconditionally,
that making a child is a blessing, a gift from the Creator.

"Be fruitful and become many and fill the earth and subdue it ..."
This is what G'd said to Adam and Eve. We are going to take a closer look at this statement.
The command "be fruitful" is difficult to fulfill, because you yourself cannot choose to be fertile or not. This 'commandment' should not be seen as a commandment, despite the imperative, but must be understood as a creation action of the Creator, a gift to the people, and equally to the animals.
This offers the possibility to survive as a species and to create a biological balance between life and death.

Many men and women suffer from their infertility.

"... grow to many and fill the earth ..."
In the creation model there are initially two people. At that point, the command is understandable. The intention is that there will be many more people, complete peoples. If this were to go on indefinitely, then really and inevitably a kind of saturation does occur: every square meter of all existing land would be stuffed with people.

Suppose each man fathers two children and there is no war , hunger and killing deseases, then:
2 4 8 16 32 64 128 256 512 1.024 2.048 4.096 8.192 16.384 32.768 65.536 131.072 262.144 524.288 1.048.576 2.097.152 4.194.304 8.388.608 16.777.216 33.554.432 67.108.864 134.217.728 268.435.456 536.870.912 1.073.741.824 2.147.483.648 4.294.967.296 8.589.934.592 17.179.869.184 34.359.738.368 68.719.476.736 137.438.953.472 274.877.906.944 549.755.813.888 1.099.511.627.776 2.199.023.255.552 4.398.046.511.104 8.796.093.022.208 17.592.186.044.416 35.184.372.088.832 70.368.744.177.664 140.737.488.355.328 281.474.976.710.656 562.949.953.421.312 ...

That disaster can never be the intention!

When each man fathers more children, the grow of the population increases much faster.
Try yourself 5 25 125 625 ... .

The same reasoning applies to the command "Go and multiply".
This motivation argues in favor of contraceptives.

Some peoples believe they have to father many children in a particular country. However, the question is, whether that country can produce enough food and provide adequate housing. This way, Islam tries to achieve majority with their religion.

When a man fathered at least one child and when a woman gave birth to at least one child, then these persons have already contributed to the commission "go and multiply".
Humanity then 'becomes many', but not an unwanted many.
The Chinese are well aware of this and have even instituted mandatory birth control. The debatable method is irrelevant here.

G'd promises Abram, a little later called Abraham, a Covenant between Him and his very great offspring. G'd has kept that promise.

Onan was put to death by G'd for deliberately 'wasting his seed.' The reason was, that he had to replace his deceased brother: he refused to make pregnant his sister-in-law. It is about the brother-in-law marriage.
Many interpreted it as masturbation by Onan, hence the word onanie. In the meantime it will be clear that this was a misinterpretation. Today, most peoples no longer know brother-in-law marriage or levirate.