Were All The Imams (as) Martyred?

Hadith 1:

حَدَّثَنا مُحَمَّد بن مُوسَى بن المُتِوَكِّل‏ رَضِىَ اللهُ عَنْهُ قالَ حَدَّثَنا عَلِيٍّ بن إِبراهِيم بن هاشِمٍ عَن أبِيهِ عَن أبي الصلت عَبد السلام بن صالح الهروي قالَ سَمِعتُ الرِّضا عَلَيْهِ السَّلامُ يَقُولُ: واللَّهِ مَا مِنَّا إِلا مَقْتُولٌ شَهِيدٌ

Muhammad ibn Musa ibn al-Mutawakkil - may God be pleased with him - narrated that Ali ibn Ibrahim ibn Hashem quoted on the authority of his father, on the authority of Abil Salt al-Harawi that he had heard al-Reza (عليه السلام) say,

"By Allah, None of Us is, but killed and a martyr."

[Source: Uyoon Al Akhbar Ar Riza, Chapter. 66, Hadees. 9]


Hadith 2:

There is a similar hadees from Imam Sadiq (عليه السلام) also as quoted by Allama Majlisi

وذهب كثير من أصحابنا إلى أن الائمة خرجوا من الدنيا على الشهادة، واستدلوا بقول الصادق عليه السلام: والله ما منا إلا مقتول شهيد

"And it has come from many of our companions that the Imam's (عليهم السلام) went from this world upon martyrdom and used as evidence the saying of Imam Sadiq (عليه السلام), "By Allah, None of Us is, but killed and a martyr."

[Source: Bihar Al Anwar, Allama Majlisi, Vol. 27, Pg. 209]


Hadith 3:

وأخبرني جماعة عن أبي عبد الله محمد بن أحمد الصفواني قال: حدثني الشيخ الحسين بن روح رضي الله عنه أن يحيى بن خالد سم موسى بن جعفر عليه السلام في إحدى وعشرين رطبة وبها مات، وأن النبي والأئمة عليهم السلام ما ماتوا إلا بالسيف أو السم. وقد ذكر عن الرضا عليه السلام أنه سم، وكذلك ولده وولد ولده

Shaikh al-Tusi narrates from a group of scholars from Abu Abdullah Muhammad bin Ahmad Sufwani from Shaykh Husain bin Rauh who said,

"Yahya bin Khalid poisoned Musa ibn Jafar (عليه السلام) through 21 dates and this led to His death. And The Messenger of Allah (صلى الله عليه وآله) and the Imams (عليهم السلام) did not die, except through martyrdom by sword or poison. And it is narrated from Imam Ridha (عليه السلام) that he was poisoned; as well as His Son and His Grandson."

[Source: al-Ghaybah, Shaikh Toosi, Pg. 387, Hadith. 352]