(2:30. And (remember) when your Lord said to the angels: "Verily, I am going to place (mankind) generations after generations on earth.'' They said: "Will You place therein those who will make mischief therein and shed blood, ـ while we glorify You with praises and thanks and sanctify You.'' He (Allah) said: "I know that which you do not know.'')
the tafsir ibn Kathir:
(Will You place therein those who will make mischief therein and shed blood).
The angels meant that this type of creature usually commits the atrocities they mentioned. The angels knew of this fact, according to their understanding of human nature, for Allah stated that He would create man from clay. Or, the angels understood this fact from the word Khalifah, which also means the person who judges disputes that occur between people, forbidding them from injustice and sin, as Al-Qurtubi said.
The statement the angels uttered was not a form of disputing with Allah's, nor out of envy for the Children of Adam, as some mistakenly thought. Allah has described them as those who do not precede Him in speaking, meaning that they do not ask Allah anything without His permission. When Allah informed them that He was going to create a creation on the earth, and they had knowledge that this creation would commit mischief on it, as Qatadah mentioned, they said,
(Will You place therein those who will make mischief therein and shed blood)
This is only a question for the sake of learning about the wisdom of that, as if they said, Our Lord! What is the wisdom of creating such creatures since they will cause trouble in the earth and spill blood "If the wisdom behind this action is that You be worshipped, we praise and glorify You (meaning we pray to You) we never indulge in mischief, so why create other creatures''
Allah said to the angels in answer to their inquiry,
﴿إِنِّي أَعْلَمُ مَا لاَ تَعْلَمُونَ﴾
(I know that which you do not know.) meaning, "I know that the benefit of creating this type of creature outweighs the harm that you mentioned, that which you have no knowledge of. I will create among them Prophets and send Messengers. I will also create among them truthful, martyrs, righteous believers, worshippers, the modest, the pious, the scholars who implement their knowledge, humble people and those who love Allah and follow His Messengers.''
To Qatarita
You have to understand the wisdom of Allah, remember when he said:
﴿وَإِذْ قَالَ رَبُّكَ لِلْمَلَـئِكَةِ إِنِّي جَاعِلٌ فِى الأَرْضِ خَلِيفَةً قَالُواْ أَتَجْعَلُ فِيهَا مَن يُفْسِدُ فِيهَا وَيَسْفِكُ الدِّمَآءَ وَنَحْنُ نُسَبِّحُ بِحَمْدِكَ وَنُقَدِّسُ لَكَ قَالَ إِنِّي أَعْلَمُ مَا لاَ تَعْلَمُونَ ﴾
(2:30. And (remember) when your Lord said to the angels: "Verily, I am going to place (mankind) generations after generations on earth.'' They said: "Will You place therein those who will make mischief therein and shed blood, ـ while we glorify You with praises and thanks and sanctify You.'' He (Allah) said: "I know that which you do not know.'')
the tafsir ibn Kathir:
(Will You place therein those who will make mischief therein and shed blood).
The angels meant that this type of creature usually commits the atrocities they mentioned. The angels knew of this fact, according to their understanding of human nature, for Allah stated that He would create man from clay. Or, the angels understood this fact from the word Khalifah, which also means the person who judges disputes that occur between people, forbidding them from injustice and sin, as Al-Qurtubi said.
The statement the angels uttered was not a form of disputing with Allah's, nor out of envy for the Children of Adam, as some mistakenly thought. Allah has described them as those who do not precede Him in speaking, meaning that they do not ask Allah anything without His permission. When Allah informed them that He was going to create a creation on the earth, and they had knowledge that this creation would commit mischief on it, as Qatadah mentioned, they said,
(Will You place therein those who will make mischief therein and shed blood)
This is only a question for the sake of learning about the wisdom of that, as if they said, Our Lord! What is the wisdom of creating such creatures since they will cause trouble in the earth and spill blood "If the wisdom behind this action is that You be worshipped, we praise and glorify You (meaning we pray to You) we never indulge in mischief, so why create other creatures''
Allah said to the angels in answer to their inquiry,
﴿إِنِّي أَعْلَمُ مَا لاَ تَعْلَمُونَ﴾
(I know that which you do not know.) meaning, "I know that the benefit of creating this type of creature outweighs the harm that you mentioned, that which you have no knowledge of. I will create among them Prophets and send Messengers. I will also create among them truthful, martyrs, righteous believers, worshippers, the modest, the pious, the scholars who implement their knowledge, humble people and those who love Allah and follow His Messengers.''
for the whole tafsir please read here:
http://www.qtafsir.com/index.php?option=com_content&task=view&id=407