His statement, “The Imam must”: Who is the Imam?
The Imam is the ruler—that is, the supreme authority in the state. States differ today: in some, the supreme authority is called a king; in others, a president, an emir, a sultan, or a shaykh. What matters is the reality denoted: whoever holds the highest authority in the state is the Imam.
His statement, “The Imam must”: This is because the Imam is, in reality, the successor of the Messenger of Allah, peace and blessings be upon him. The scholars differed over whether it is permissible to call someone “the successor of Allah.”
Some scholars said that it is permissible to say “the successor of Allah,” but this is an attribution of the thing to its doer; that is, one whom Allah has made a successor. In other words, Allah has appointed you as His successor on earth. It does not mean that Allah, Exalted is He, has entrusted you with the care of His servants because He is unable to manage their affairs. Certainly not. Rather, it means that Allah has made you a successor on earth, succeeding Him in relation to His servants—that is, establishing His law among them. Allah Most High said to David, peace be upon him:
“O David, indeed We have made you a successor upon the earth, so judge between the people in truth.” [Surah Sad 38:26]
A poet said, addressing Umar ibn Abd al-Aziz, may Allah have mercy on him:
The successor of Allah—then may Allah preserve him;
May the Most Merciful accompany you on your journey.
Whenever the rain has failed us,
From the Caliph we hope for what we hope from the rain.
Thus he called him “the successor of Allah,” and, according to the report, Umar approved of it and did not object.
Other scholars said that this is not permissible, because a person’s successor is appointed only when the one appointing him is absent. This is why Moses said to Aaron—peace be upon them both—