We mentioned previously that one of the good attributes and values of human beings is the possibility of being caliph or representative of Allah on His earth. This is the highest value or perfection that one may reach. Because of the importance of this subject we should speak about it more.
The term Khalifah literally means that which comes after another a successor. For example, a new generation is Khalifah of the old one.
فَخَلَفَ مِنْ بَعْدِهِمْ خَلْفٌ أَضَاعُوا الصَّلَاةَ وَاتَّبَعُوا الشَّهَوَاتِ فَسَوْفَ يَلْقَوْنَ غَيًّا
“But there came after them an evil generation, who wasted the prayer, and followed lusts; so they shall encounter error.” (19:59).
Those people who were rulers after the Prophet (S) were called 'Khalifat al-Rasul', meaning successor of the Prophet, such as Imam Ali (‘a). So what does 'Khalifat Allah' mean? Every person chosen by Allah to be His representative on earth is called Caliph. They are chosen by Allah to lead people, to judge between them and to guide them, because it is not possible for all people to receive Divine laws by themselves or to judge.
One of the verses in the Glorious Qur'an about this position is the following verse.
يَا دَاوُودُ إِنَّا جَعَلْنَاكَ خَلِيفَةً فِي الْأَرْضِ فَاحْكُمْ بَيْنَ النَّاسِ بِالْحَقِّ وَلَا تَتَّبِعِ الْهَوَىٰ فَيُضِلَّكَ عَنْ سَبِيلِ اللَّهِ إِنَّ الَّذِينَ يَضِلُّونَ عَنْ سَبِيلِ اللَّهِ لَهُمْ عَذَابٌ شَدِيدٌ بِمَا نَسُوا يَوْمَ الْحِسَابِ
“O Dawud! Surely we have made you a viceroy (Khalifah) in the land; so judge between men with justice and do not follow desire, lest it should lead you astray from the path of Allah; (as for) those who go astray from the path of Allah, they shall surely have a severe punishment because they forgot the day of reckoning.” (38:26).
This verse was revealed after a certain event. God wanted to test Dawud (‘a). The story is expressed in the previous verses, i.e., 38:21-25. Finally Allah made him His representative on earth and then a judge. According to the monotheistic view of the Glorious Qur'an no one has authority over people and the fight to judge among people, unless assigned or approved by Allah.
If someone is knowledgeable, it does not mean he can judge. Allah has the fight to judge and He appoints prophets. Prophets can also appoint others. There are many traditions of our Imams in which they explain that a person who has some qualities such as justice and ability to understand Islamic laws directly (ijtihad) can also judge as they are appointed by the Imams. So, there are two types of appointment: General appointment which is due to the possession of certain qualities, and special appointment in which some particular person is appointed and his name is mentioned.
So Dawud (‘a) was one of the representatives of Allah on earth. Another case is found in the following verse.
وَإِذْ قَالَ رَبُّكَ لِلْمَلَائِكَةِ إِنِّي جَاعِلٌ فِي الْأَرْضِ خَلِيفَةً قَالُوا أَتَجْعَلُ فِيهَا مَنْ يُفْسِدُ فِيهَا وَيَسْفِكُ الدِّمَاءَ وَنَحْنُ نُسَبِّحُ بِحَمْدِكَ وَنُقَدِّسُ لَكَ قَالَ إِنِّي أَعْلَمُ مَا لَا تَعْلَمُونَ
“And when your Lord said to the angels, I am going to place in the earth a Khalifah, they said: what! Will You place in it such as shall make mischief in it and shed blood, and we celebrate Your praise and extol Your holiness? He said: surely I know what you do not know.” (2:30).
Here, a question arises that when God appointed a Khalifah (according to the verse 2:30), was that appointing exclusive to Adam (‘a) or not? The answer is negative. As we saw before Dawud (‘a) was Khalifah. Certainly Moses (‘a), Jesus (‘a), the Noble Prophet (S) and some other prophets were also Khalifah. Some scholars use the following verse as one of their reasons to prove that it was not exclusive to Adam (‘a).
وَهُوَ الَّذِي جَعَلَكُمْ خَلَائِفَ الْأَرْضِ وَرَفَعَ بَعْضَكُمْ فَوْقَ بَعْضٍ دَرَجَاتٍ لِيَبْلُوَكُمْ فِي مَا آتَاكُمْ
“And He is who has made you successors in the land and raised some of you above others by (various) grades, that He might try you by what He has given you.” (6:165).
Now let's go back to the verse 2:30. When we observe what the angels said, we find out that the appointment was not exclusive to Adam, because they said: “What! Will You place in it such as shall make mischief in it and shed blood...?”(2:30). Those angels could not be afraid of Adam (‘a). And if this position given to human beings was not so important, they would not protest or question Allah and they would not say: “What! Will You place in it... and we celebrate Your praise and extol Your holiness?”
So this is the conclusion: Allah wanted to appoint representatives of Himself on earth. The angels understood firstly, that this position is very high, secondly, that it was not exclusive to Adam (‘a), and thirdly, that Allah wanted to make a new species on earth and among them some will be good and some will be bad and amongst those good human beings will be some at this high position (caliphate) and they will be rulers on earth or the natural universe. As a result, the angels wished that they had that closeness to Allah, because they were aware of their own goodness and they observed only negative points of human beings. Answering them Allah said: 'I know what you do not know” (2:30). When Allah wanted to show the angels the merits of human beings, He taught Adam (‘a) all the names. Let's follow this part of the problem through the following verses.
وَعَلَّمَ آدَمَ الْأَسْمَاءَ كُلَّهَا ثُمَّ عَرَضَهُمْ عَلَى الْمَلَائِكَةِ فَقَالَ أَنْبِئُونِي بِأَسْمَاءِ هَٰؤُلَاءِ إِنْ كُنْتُمْ صَادِقِينَ
“And He taught Adam all the names, then presented them to the angels; Then He said: Tell me the names of those if you are right.” (2:31).
قَالُوا سُبْحَانَكَ لَا عِلْمَ لَنَا إِلَّا مَا عَلَّمْتَنَا إِنَّكَ أَنْتَ الْعَلِيمُ الْحَكِيمُ
“They said: Glory be to You! We have no knowledge but that which You have taught us; surely You are the Knowing, the Wise.” (2:32).
قَالَ يَا آدَمُ أَنْبِئْهُمْ بِأَسْمَائِهِمْ فَلَمَّا أَنْبَأَهُمْ بِأَسْمَائِهِمْ قَالَ أَلَمْ أَقُلْ لَكُمْ إِنِّي أَعْلَمُ غَيْبَ السَّمَاوَاتِ وَالْأَرْضِ وَأَعْلَمُ مَا تُبْدُونَ وَمَا كُنْتُمْ تَكْتُمُونَ
“He said: 'O Adam! Inform them of their names. Then when he had informed them of their names, He said 'Did I not say to you that I surely know what is hidden (ghayb) in the heavens and the earth and (that) I know what you manifest and what you hide?” (2:33).
So at least one of condition of being Khalifah of Allah is conclusive knowledge. According to Shi'ism all the fourteen infallibles had this knowledge. We say:
السلام عليك يا خليفة الله في أرضه
“Peace be with you, O representatives of Allah on earth.”
When a person is chosen to be Khalifah, he at least has one of two types of guardianship (Wilayat):
a) Guardianship over the universe and creatures. Having this kind of guardianship one can do everything in this world such as reviving the dead, curing the sick. It is called 'generative (takwini) guardianship.
b) Guardianship in judgement and making Jaws. Ordinary people can never make laws. Even a mujtahid cannot make any law and his job is just to refer to Islamic sources and understand practical laws. Also Islamic parliament cannot make some laws instead of Divine laws. They try their best to apply general laws to different situations and if they make some laws, they are really filling empty places in the legislative universe which is delegated to them by Allah (to the people or to the legal authority). This kind of guardianship is called 'legislative (tashri’i) guardianship' .
According to the verse (38:26) Dawud (‘a) had this kind of guardianship. Adam (‘a) was khafffah on earth while perhaps there was no need for laws or judgements (for a further discussion of the very point look at comments on the verse 2:21).
So at least his actual guardianship was generative. But after deeper study it will be obvious that every representative of Allah was allowed to apply his guardianship in both aspects: generative and legislative, if necessary and possible.