Abu Hurairah said: “By the One Whom there is no god but him, if Abu Bakr had not been appointed as Caliph then Allah would not have been worshipped.” 
“All pious Muslims well-read in the Hadith (the compiled sayings of the Prophet) firmly believe in the need to establish an Islamic State headed by a Muslim Caliph. This is mentioned twice in the Holy Quran and it’s central to the Islamic faith. No Muslim scholar would debate an Islamic state and the caliphate. Muslim Sunnis claim that the caliph should hail from Meccan notability. Shiite Muslims add that he must be from Ahl al-Bayt; a member of the prophet’s family.” (Sami Moubayed, Daily Telegraph, 23 Sep 2015)
This is an extract from the book Al-Jihad wa’l Qital fi as-Siyasa ash-Shar’iyya by Sheikh Muhammad Khayr Haykal, chapter ‘The Sixth Study: Al‐Qitaal against the deviation of the ruler.’
The Messenger of Allah ﷺ said: سَتَكُونُ أُمَرَاءُ فَتَعْرِفُونَ وَتُنْكِرُونَ فَمَنْ عَرَفَ بَرِئَ وَمَنْ أَنْكَرَ سَلِمَ وَلَكِنْ مَنْ رَضِيَ وَتَابَعَ . قَالُوا أَفَلاَ نُقَاتِلُهُمْ قَالَ لاَ مَا صَلَّوْا “‘There will be ameers, you recognise (something of what they do) and you reject (some). Whosoever recognised, he would be absolved (of sin) and whosoever rejected, he would be safe. But whosoever accepted and followed (what they do, he would not be safe).’ They (the Sahabah) asked ‘Shouldn’t we fight them?’ He said; ‘No, as long as they pray.’” (Sahih Muslim 1854a)
BY ABU YUSUF In the Qur’an, I have found several examples of people who achieved incredible things but their names and background are not mentioned at all.
BY MAZIN ABDUL-ADHIM Many people have asked me to provide more details behind why the leadership of Hizb ut Tahrir verified the moon sighting and declared that Eid will be today (Tuesday). I contacted the head of the media office and received a clarification. But before listing the specific eyewitness accounts, I would like to point out something very important first:
BY NABEEL ALKHALIDY. THIS HAS BEEN REPRODUCED FROM THE SIBAWAY INSTITUTE. This tafseer shows how the Qur’an prophesies the establishment of the Zionist state of Israel and its future destruction at the hands of the believers. Israel will never be challenged or removed by the current regimes in the Muslim world who are its biggest protectors. Rather only with their removal and replacement with a Khilafah will the Muslims of Palestine finally find the justice they have been waiting decades for.