Yahya related to me from Malik from Thawr ibn Zayd ad-Dili that
Allah, the Blessed, the Exalted, sent down about a man who divorced
his wife and then returned to her while he had no need of her and did
not mean to keep her so as to make the idda period long for her by
that in order to do her harm, "Do not retain them by force, to
transgress. Whoever does that has wronged himself." (Sura 2 ayat 231).
Allah warns them by that ayat.
Muwatta Malik Book 29, Hadith 89