It is a supplication narrated by Sheikh Tusi in Kitab al-Tahdhib by Safwan Jammal. Imam Sadiq (a.s.) told me about Arbaeen supplication: When a significant part of the day is over, read this supplication:
Peace be upon the intimate servant of Allah and His most-beloved.
Peace be upon the friend of Allah and His elite.
Peace be upon the choice of Allah and son of His choice.
Peace be upon al-Husayn the wronged and martyred.
Peace be upon the captive of agonies and victim of the shed tears.
O Allah, I do bear witness that he is verily Your intimate servant and son of Your intimate servant,
Your choice and son of Your choice,
and the winner of Your honoring.
You have honored him with martyrdom,
endued him with happiness,
privileged him with legitimate birth,
and made him a master among the masters,
a leader among the leaders,
a treasure among the treasures,
and gave him the inheritance of the prophets
and made him a proof over Your creation from among the successors.
So he was sincere in supplication
and generous in advice
and put his heart, mind, soul and life at Your disposal
to liberate Your servants from ignorance
and confusion of misguidance
and he was confronted by those whom the world had deceived
and who sold their share for the lowest price
and bought their hereafter for the cheapest value
and became arrogant and rebellious in their desires
and angered You and angered Your prophet,
and obeyed from among Your servants the people of enmity and hypocrisy
and the bearers of burdens who deserve the fire [of hell].
So he fought them for Your sake patiently and expectantly
until his blood was spilled in Your obedience
and his sanctity was violated.
O Allah, so curse them a severe curse
and punish them with a painful punishment.
Peace be upon you, O son of the messenger of Allah.
Peace be upon you, O son of the master of the successors.
I bear witness that you are the trustee of Allah and son of His trustee,
you lived happily and died praiseworthily
and departed as a martyr and wronged one.
And I bear witness that Allah will fulfill His promise to you
and destroy those who wronged you
and punish those who killed you.
And I bear witness that you are verily a light in the lofty loins
and pure wombs [that were never] defiled by impurities
nor were you covered by the darknesses of its clothes.
And I bear witness that you are one of the pillars of religion
and one of the signs of guidance
and one of the strong ropes
and one of the proofs over the people of this world.
And I bear witness that I believe in you
and I am certain about your return
by my religion’s laws and my deeds’ conclusions
and my heart is at peace with your heart
and my affair follows your affair
and my support for you is ready
until Allah permits you to appear.
So with you, with you, not with your enemy.
May Allah’s blessings be upon you and upon your souls and bodies [or forms]
and your witnesses and absent ones
and your apparent and hidden ones.
Amen, Lord of the worlds.
