Is Sufism part of Islam, or separate from it?

Sufism is part of Islam, its inner dimension. To claim Sufism is outside Islam is to take the soul out of our religion.

What are Islam, Iman, and Ihsan, and where does Sufism fit?

The religion of Islam is composed of three fundamentals: Islam, external compliance with what Allah asks of us; Iman, the belief in the unseen that the Prophets have informed us of; and ihsan, to worship Allah as though one sees Him. The level of Iman is the Aqida, Islam is the Shariah and its ancillary disciplines, and the level of ihsan is Tasawwuf. All three are named in the Prophet's answers when Jibril questioned him.

Is Sufism a bid’ah (innovation), since the word isn’t found in the Qur’an?

The absence of its name from the Qur'an does not make Sufism a bid'ah: many essential Islamic sciences, Tafsir, hadith science, theology, got their names only after the first generation. A thing is not bid'ah if the Shariah itself supports its purpose.

Aren’t the Qur’an and Sunnah enough, why do we even need Tasawwuf?

The superiority of the Qur'an and Sunnah is not in question. Tasawwuf is the practice of applying them, since knowledge is not sufficient in itself. Knowledge of the Qur'an and Sunnah does not suffice until it is lived.

Do you have to be a Muslim to be a Sufi? Can anyone be a Sufi?

The belief often held in the West that Sufism is universal and a person from any religion can be a Sufi is a delusion. Without the Shahadah, correct belief, following the Shariah and the Prophetic Sunnah, no one can attain the pleasure of Allah; one who does not truly believe in any of the fundamental tenets cannot be a Muslim, and Tasawwuf does not exist without the Shahadah and the Shariah.

Do Sufis have to follow the Shariah?

Tasawwuf entails that life be spent according to the Shariah, and any “Tasawwuf” that sets itself against the Shariah is irreligious and rejected.

Is Sufism the same as monasticism? Do Sufis withdraw from the world?

Islam does not permit monasticism; Tasawwuf calls a person to live fully in the world, as a good son, a good father, a good husband, neighbour, and employee, not to retreat from it.

Can a Sufi marry, work, and raise a family?

In Tasawwuf the seeker is not barred from having children or running a successful business. Your sleep, your time with family, and your lawful earning are part of your spiritual path only if done with the intention to please Allah.

What is the real meaning of Zuhd (detachment / asceticism)?

Zuhd does not mean forbidding what is permitted or squandering wealth; rather, it means trusting what is in Allah's hand more than what is in your own, and meeting hardship with patience.

Is a Sufi like a Hindu Yogi? Is Sufi practice just meditation or yoga?

The Sufi and the Hindu Yogi are opposites. A Sufi seeks Allah; the Yogi detracts from the very existence of Allah toward Nirvana. The assertion that their rigors are similar is completely fake: a Sufi's training has its origin only in Islam.