Short answer
No. Calling your wife "sister" is not a divorce, though it is disliked. "You are like my mother" depends on your intention: as respect it means nothing, as divorce it is a talaq. "You are to me like my mother's back" is zihar, which forbids intimacy until you pay its expiation: fasting two months in a row, or feeding sixty poor people if you cannot fast.
Calling her 'my sister' or 'my mother' is makruh but has no legal effect. 'You are like my mother' is judged by intention: respect means nothing, divorce means one final talaq, and zihar means zihar. Likening her to the back, or another part that may not be looked at, of a woman permanently forbidden to him is clear zihar: intimacy and its preliminaries become haram until he performs the kaffarah.
The four schools agree on this.
Explanation
Before Islam, a man could end his marriage by saying, "You are to me like my mother's back" (zihar), leaving the wife neither married nor free. When Khawlah bint Tha'labah complained about this to the Prophet ﷺ, Allah revealed Surah al-Mujadilah: wives "are not their mothers... and indeed they are saying an objectionable statement and a falsehood" (58:2). Zihar no longer ends a marriage, but it is a sin with a heavy expiation.
What different words mean in the Hanafi school:
- "My sister" or "sis" in conversation: no talaq and no zihar, but disliked, because it echoes zihar. Use her name or a kind word instead.
- "You are like my mother": depends on intention. If you meant honour or affection, nothing happens. If you meant divorce, one final talaq. If you meant zihar, it is zihar.
- "You are like my mother's back" or similar: zihar, whatever the intention.
The kaffarah of zihar (58:3 to 4): freeing a slave, which is not possible today; otherwise fasting two consecutive months before any intimacy; and if he truly cannot fast, feeding sixty poor people. Intimacy before completing it is a further sin that needs tawbah. The kaffarah calculator helps with the feeding amount.
Words about marriage carry weight. If you are unsure what you said or meant, ask a mufti with the exact words. See the words of talaq and talaq as a joke.
Ask a mufti about your own case. This answer explains the general ruling. When the details of your situation matter, as they do here, ask a qualified mufti and give them the full facts. Where to ask a scholar.
The evidence
Quran, Surah Al-Mujaadila 58:2
ٱلَّذِينَ يُظَٰهِرُونَ مِنكُم مِّن نِّسَآئِهِم مَّا هُنَّ أُمَّهَٰتِهِمْ ۖ إِنْ أُمَّهَٰتُهُمْ إِلَّا ٱلَّٰٓـِٔى وَلَدْنَهُمْ ۚ وَإِنَّهُمْ لَيَقُولُونَ مُنكَرًۭا مِّنَ ٱلْقَوْلِ وَزُورًۭا ۚ وَإِنَّ ٱللَّهَ لَعَفُوٌّ غَفُورٌۭ ﴿٢﴾
Those who pronounce thihar among you [to separate] from their wives - they are not [consequently] their mothers. Their mothers are none but those who gave birth to them. And indeed, they are saying an objectionable statement and a falsehood. But indeed, Allah is Pardoning and Forgiving.
Zihar does not make a wife a mother and is a false statement.
Quran, Surah Al-Mujaadila 58:3
وَٱلَّذِينَ يُظَٰهِرُونَ مِن نِّسَآئِهِمْ ثُمَّ يَعُودُونَ لِمَا قَالُوا۟ فَتَحْرِيرُ رَقَبَةٍۢ مِّن قَبْلِ أَن يَتَمَآسَّا ۚ ذَٰلِكُمْ تُوعَظُونَ بِهِۦ ۚ وَٱللَّهُ بِمَا تَعْمَلُونَ خَبِيرٌۭ ﴿٣﴾
And those who pronounce thihar from their wives and then [wish to] go back on what they said - then [there must be] the freeing of a slave before they touch one another. That is what you are admonished thereby; and Allah is Acquainted with what you do.
Zihar needs an expiation before intimacy resumes.
Where the ruling is recorded
- al-Hidaya, Kitab al-Talaq, Bab al-Zihar. The forms of zihar, the effect of intention in 'you are like my mother', and the kaffarah.
- Radd al-Muhtar (Ibn Abidin), Bab al-Zihar. Calling a wife 'my sister' is makruh and has no effect.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.