Ibn Majah

1:
This means that the process of “writing down hadith” began during the blessed life of the Prophet sallallahu alayhi wa sallam, just as it did with the Qur’an. It is established by dozens of authentic narrations that the Messenger of Allah sallallahu alayhi wa sallam himself had his statements, commands, and rulings written down (apart from the Qur’an), and he had also granted permission to twenty Companions radi Allahu anhum to write down the blessed hadith.
(For details, see the chapter “What has come regarding the concession for writing knowledge” in the Book of Knowledge from the Messenger sallallahu alayhi wa sallam.)

2:
This ruling applies to both the owners of the animals and the collectors of zakat.
The situation of combining what is separate is, for example, if three people each have forty goats kept separately, then zakat of one goat is obligatory on each.
When the zakat collector comes, all three combine their goats out of fear of zakat so that only one goat has to be given.

3:
Its explanation is as follows: for example, there are two partners, each has one hundred and one goats, making a total of two hundred and two goats.
There is zakat due on three goats among them.
When the zakat collector comes, both separate their goats so that only one is obligatory on each. Doing so is prohibited.

4:
For example, there are two partners:
One has one thousand goats and the other has only forty goats.
Thus, the total is one thousand and forty goats. The zakat collector comes and takes ten goats as zakat.
Suppose the price of each goat is twenty-six rupees,
thus their total value is two hundred and sixty rupees, of which ten rupees will be the responsibility of the one who owns forty goats, and two hundred and fifty rupees will be upon the one who owns one thousand goats.
Because in one thousand and forty, there are twenty-six forties, of which the zakat of one forty will be upon the owner of forty goats, and the zakat of twenty-five forties will be upon the owner of one thousand goats. Now, if the zakat collector has taken ten goats from the goats of the one who owns forty goats, whose total value is two hundred and sixty rupees, then the one with a thousand goats will return two hundred and fifty rupees to him. And if the zakat collector has taken from the goats of the one who owns a thousand goats, then the one with forty goats will return ten rupees to him.

Note:
(In the chain, Sufyan ibn Husayn is a trustworthy narrator,
but there is some discussion regarding his narration from Ibn Shihab al-Zuhri,
however, on the basis of corroborating narrations and supporting evidence, this hadith is also authentic.)

1568. Commentary: If there are three hundred goats, then three goats will be due as zakat, up to three hundred and ninety-nine. If there are four hundred in total, then four goats will be due, up to four hundred and ninety-nine. And so on, following this pattern.

Benefits and Issues:

➊
If two people combine their goats to form a single flock, they are called "khalit" (partners in mixture).
This partnership is considered valid when both flocks have a common shepherd, enclosure, water arrangement, and a shared male goat for breeding. (Muwatta Imam Malik, Zakat, Chapter: Charity of Partners: 1/242)
If the partnership is such that each party has its own goats, this is called "khulta" (mixing).
If every goat is jointly owned—for example, two people pool their money to buy several goats—this is not "khulta" but "shirkah" (partnership).
An example of accounting on the basis of equality is that two individuals, each owning forty goats, mix their flocks to make one herd.
If the zakat collector takes a goat from one person's share as zakat, the other person will pay him half the price of a goat.
If there is a difference in the number of goats, they will settle accounts with each other proportionally.
If the zakat payer willingly wants to give a superior animal or a male goat, it may be accepted, but the zakat collector should not demand it himself.
If the word is read as "musaddiq" (zakat collector), the meaning will be that if the official, for some benefit, prefers to take a defective or old animal, the zakat payer is not sinful. For example:
It is possible that an animal is lame, but it has more meat, or because it is of a superior breed, it is considered better than other animals. In this way, the public treasury (bayt al-mal) or the deserving recipient who receives it will benefit more.

Benefits and Issues:
➊ A cow or she-camel gives birth to one offspring at a time, but goats give birth to more offspring, which is why there are more kids in a flock of goats. In view of this, the Shariah has set a lower rate of zakat for goats. If the total number of goats in the flock, including the kids, is less than forty, then no zakat is obligatory on this wealth. For a number between forty and one hundred and twenty, the zakat is only one goat. For a flock numbering from one hundred and twenty-one to two hundred, it is obligatory to pay two goats as zakat. For a number from two hundred and one to three hundred and ninety-nine, the amount of zakat is three goats. When the number reaches four hundred, four goats will be given and received. For any number above this, for every complete hundred, one goat will be due as zakat. There is no zakat on goats exceeding the complete hundreds.

The case of combining separate flocks is as follows, for example: Two people each had forty goats, on which each flock was liable for one goat as zakat. They had to pay a total of two goats. They combined their goats to make one flock. In this way, for eighty (80) goats, only one goat was given as zakat, thus saving one goat. When the zakat collector left, both separated again. An example of making two flocks from one to save zakat is that two people had a joint flock of two hundred and twenty goats, so three goats were due as zakat. They divided them into two flocks, each with one hundred and ten goats. In this way, one goat became obligatory for each flock, and a total of two goats were given as zakat, saving one goat. Or, if there were sixty goats in a flock, on which one goat is due as zakat, they divided them into two flocks of thirty each, on which no zakat is due.

The act of making one flock into two, or combining two flocks into one, can also be done by the zakat collecting officer (ʿāmil) in order to collect more zakat, but this is also prohibited. An example of this is dividing one hundred goats into two groups of fifty each so that two goats are collected instead of one, or considering two flocks as one, each of which has one hundred and fifteen goats, so that two goats are collected, or considering two flocks as one, each of which has one hundred and fifteen goats, so that instead of two goats, three goats are collected.

By "sānde" is meant the male animal kept in the flock for breeding purposes. Its importance lies in the fact that it is valuable to the owner, whereas an old or defective animal, if given to a deserving recipient, would be considered a deprivation of their right, because they would not be able to benefit fully from it. This ruling has been given so that neither the zakat giver is harmed nor the zakat recipient.