What is the required immediacy for writing down one's will?

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Every Muslim who possesses something worth bequeathing must ensure their will is written down before they sleep for two successive nights. This obligation is derived from the Hadith reported by Ibn Umar, where the Messenger of Allah (peace be upon him) said, "It is not fitting for a Muslim man who has something to bequeath to spend two nights without his will being written down with him." This is agreed upon (Muttafaqun Alayhi).