Ash-Shaykh Abdul Azeez ar-Raajihi, may Allah preserve him, was asked the following question,
لسؤال: ذكرتم بعض فوائد السواك، وذكرتم أنه يساعد في النطق بالشهادة في حالة الاحتضار، فهل هذا ثابت وصحيح؟
When you mentioned some of the benefits of using the siwaak, you mentioned that it helps in uttering the shahaadah (i.e. the word la ilaha illallah) when dying. So has this been proven and is it authentic?
الإجابة: نعم ذكر العلماء أن من فوائده أنه يذكر الشهادة عند الموت، هذا ذكره أهل العلم قالوا: إن هذا من فوائده، وإنه ثابت. نعم.
Yes, the scholars have mentioned (that) from its (the miswaak’s) benefits is that the individual will be able to say the shahaadah when dying. This is something the people of knowledge have mentioned; they said (that) verily this is from its benefits and it is something proven, yes.”
Reference: The Fataawa of Ash-Shaykh Abdul Azeez ar-Raajihi (an excerpt from the fataawa app).
[Reference removed since it no longer exists]
This is something I found interesting, and likewise I found some of the Shaafi’i scholars mention this. However, I haven’t found any proof for this yet. Allah knows best.
AbdulFattaah bin Uthman