What is tawbah? How do I repent sincerely in Islam?

"This too is not repentance from repentance, but rather repentance from the lack of repentance. The portion of repentance that exists is an act of obedience that should not be repented from, while the missing portion is what requires repentance. Repentance from repentance can only be understood in one of these two ways."

"The type coupled with repentance is illustrated by اللّٰه's words: "Seek forgiveness from your Lord and then repent to Him, He will let you enjoy a good provision for a specified term and give every doer of favor his favor." And the words of هُود to his people: "Seek forgiveness from your Lord and then repent to Him, He will send rain from the sky upon you in continuing showers." And the words of صَالِح to his people: "He has produced you from the earth and settled you in it, so seek forgiveness of Him and then repent to Him."

"This is an illogical statement and not correct in itself. There might be a flaw, deficiency, or impediment in the repentance that prevents its perfection. The person may or may not be aware of this, and they should repent from the deficiency in their repentance and from not fulfilling its rights. This too is not repentance from repentance, but rather repentance from the lack of repentance."

"What they repent from might be considered among the greatest good deeds of others. In summary, the repentance of the true lovers who are knowledgeable of their Lord and His rights is the true repentance, while others are veiled from it. Beyond this is another repentance, which we should turn away from discussing. Chapter: The author of "Al-Manazil" explains that the station of repentance is not fully realized until one repents from everything other than the Truth, perceives the cause of repentance, and then repents from even seeing that cause."

"Al-Fudayl also said, "Seeking forgiveness without giving up the sin is the repentance of liars. Rabiah al-Adawiya remarked, "Our seeking forgiveness needs much seeking forgiveness." Some wise people observed, “Whoever seeks forgiveness without regret is mocking Allah, the Exalted, while he does not realize it. A Bedouin was heard clinging to the curtains of the Kaaba, saying, "O Allah, truly my seeking forgiveness while persisting is a betrayal, and abandoning seeking Your forgiveness while knowing Your vast pardon is weakness."

"I seek the forgiveness of Allah and repent to Him in a day seventy times," even though his past and future sins were forgiven. He also mentioned, "Indeed, there is a veil upon my heart, and I seek the forgiveness of Allah a hundred times in a day." The Prophet, peace be upon him, advised, "Whoever says, when retiring to bed, 'I seek forgiveness of Allah, the Almighty, Whom there is none worthy of worship except Him, the Living, the Sustainer, and I repent to Him' three times, Allah will forgive him his sins even if they were as much as the foam of the sea, the grains of sand in a desert, the leaves of trees, or the days of the world."

"Hudhayfah once said, "I was sharp-tongued with my family, so I said, 'O Messenger of Allah, I fear my tongue will lead me to the Fire. The Prophet, peace be upon him, replied, 'Where are you from seeking forgiveness? Indeed, I seek the forgiveness of Allah a hundred times in a day.'" 'A'isha, may Allah be pleased with her, reported that the Messenger of Allah, peace be upon him, said to her, "If you commit a sin, seek Allah’s forgiveness and repent to Him, for repentance from sin is regret and asking for forgiveness.""

"He said: "Allah the Exalted says: 'O My servants, you all sin by day and by night, and I forgive all sins, so ask Me for forgiveness and I will forgive you. And whoever knows that I have the power to forgive him, I forgive him, and it does not bother Me.'" The Prophet, peace be upon him, said: "Whoever says, 'Glory be to You, I have wronged myself and committed an evil deed, so forgive me, for no one forgives sins except You,' his sins will be forgiven, even if they were numerous as the froth of the sea.""

"the servitude of enjoining good and forbidding evil, the servitude of patience, opposing desires, and preferring the pleasures of the Lord over one's own desires. Another form of servitude is repentance, returning to Him, and seeking His forgiveness. Indeed, He, the Exalted, loves those who repent and loves their repentance. If the causes for repentance were absent, the servitude of repentance and seeking forgiveness would be inactive."

""The one who seeks forgiveness from a sin while persisting in it is like one who mocks the signs of Allah. Some would say, "I seek Allah's forgiveness from saying 'I seek Allah's forgiveness. It is said, "Seeking forgiveness with the tongue is the repentance of liars. Rabi'a al-Adawiya said, "Our seeking forgiveness itself needs a great deal of seeking forgiveness."