Hasan (may Allah have mercy on him) said: When a man makes a bequest for someone and that person is not present, then if the bequest is presented to him (the legatee) and he accepts it, the one who made the bequest no longer has the right to revoke it.
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3278
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):الوضاح بن يحيى سيئ الحفظ ولكنه متابع عليه، [مكتبه الشامله نمبر: 3289]
Hadith Takhrijاس اثر کی سند میں وضاح بن یحییٰ سئی الحفظ ہیں، لیکن اوپر اس معنی کے شواہد گذر چکے ہیں۔
Brief Explanation
(Commentary on Ahadith 3274 to 3278)
The person to whom a bequest (wasiyyah) is made has the choice to accept or reject it. However, once he accepts it, then the one making the bequest (the testator) cannot retract it, because this would fall under the category of giving something and then taking it back, for which there is the Prophetic command: «اَلْعَائِدُفِيْهِبَتِهِكَالْكَلْبِيَعُوْدُفِيْقَيْئِهِ. (وقانا اللّٰه منها)».