al-Moulakhas al-Fiqhi - Salih Al-Fawzan - (2/399)

he regrets the divorce and wishes to resume life with his wife, he finds the door still open before him—and that is part of Allah’s mercy to His servants.

As for the conditions that make a revocation (rajʿah) valid, they are six:

The divorce must be fewer than the number of pronouncements the husband owns: a free man must have issued fewer than three divorces, and a slave fewer than two. If he has exhausted the number he owns, she does not become lawful for him again until she marries another husband.
The woman must be one with whom consummation has taken place. If he divorces her before consummation, he has no right of rajʿah because she has no waiting-period (ʿiddah), as Allah says: “O you who believe! When you marry believing women and then divorce them before you have touched them, they have no waiting-period for you to count” (33:49).
The divorce must not be in exchange for compensation. If it was pronounced for compensation, she does not become lawful for him again except with a new contract and with her consent, for she only offered the compensation to release herself, and her purpose is not fulfilled if the husband still retains the right of revocation.
The marriage itself must have been valid. If the divorce took place in an invalid (fāsid) marriage, there is no rajʿah, for the divorce immediately separates the two.
The revocation must occur within the waiting-period, as Allah says: “Their husbands have a better right to take them back during that period” (2:228)—meaning while the ʿiddah is still in force.
The revocation must be immediate and unconditional; it is not valid if it is suspended on a future event, such as a husband saying, “If such-and-such happens, I have taken you back.”

A further question remains: must both spouses intend reconciliation when the rajʿah is made?

ندم على الطلاق وأراد استئناف العشرة مع زوجته، فيجد الباب مفتوح اأمامه، وهذا من رحمة الله بعباده". وأما شروط صحة الرجعة؛ فهي: أولاً: أن يكون الطلاق دون ما يملك من العدد؛ بأن طلق حر دون الثلاث، وعبد دون اثنتين، فإن استوفى ما يملك من الطلاق؛ لم تحل له حتى تنكح زوجا غيره. ثانيا: أن يكون المطلقة مدخولاً بها، فإن طلقها قبل الدخول؛ فليس له رجعة؛ لأنها لا عدة ع ليها؛ لقوله تعالى: ﴿يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا نَكَحْتُمُ الْمُؤْمِنَاتِ ثُمَّ طَلَّقْتُمُوهُنَّ مِنْ قَبْلِ أَنْ تَمَسُّوهُنَّ فَمَا لَكُمْ عَلَيْهِنَّ مِنْ عِدَّةٍ تَعْتَدُّونَهَا﴾ . ثالثا: أن يكون الطلاق بلا عوض، فإن كان على عوض؛ لم تحل له إلا بعقد جديد برضاها؛ لأنها لم تبدل العوض إلا لتفتدي نفسها منه، ولا يحصل مقصودها مع ثبوت الرجعة. رابعا: أن يكون النكاح صحيح ا، أما إن طلق في نكاح فاسد؛ فليس له رجعة؛ لأنها تبين بالطلاق. خامسا: أن تكون الرجعة في العدة؛ لقوله تعالى: ﴿وَبُعُولَتُهُنَّ أَحَقُّ بِرَدِّهِنَّ فِي ذَلِك﴾ ؛ أي: أولى برجعتهن في حالة العدة. سادسا: أن تكون الرجعة منجزة؛ فلا تصح معلقة؛ كما لو قال: إذا حصل كذا؛ فقد راجعتك. وهل يشترط يقصد الزوجان بالرجعة الإصلاح؟: