I needed to know incase there is any dua while washing clothes to make them purify for namaaz /anything for that matter like incase a person is going for hajj.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

As far as we are aware of, in Islamic religion there is no supplication which one should say when washing and purifying the clothes for the prayer or when washing and purifying the clothes that one intends to take with him for Hajj.

If by your question you refer to a special supplication for going to Hajj, we are not aware also of any supplication for this purpose.

What is legislated for a pilgrim to say when he starts his travel from his country is to supplicate with the supplication one says when travelling as when the Prophet would start a journey, after getting on his horse, he would say: “Allaah is the greatest, Allaah is the greatest, Allaah is the greatest, How perfect He is, The One Who has placed this (transport) at our service, and we ourselves would not have been capable of that, and to our Lord is our final destiny. 

O Allaah, we ask You for birr and taqwa [Please refer to the definition hereunder] in this journey of ours, and we ask You for deeds which please You.  O Allaah, facilitate our journey and let us cover its distance quickly.  O Allaah, You are The Companion on the journey and The Successor over the family, O Allaah, I take refuge with You from the difficulties of travel, from having a change of hearts and being in a bad predicament, and I take refuge in You from an ill fated outcome with wealth and family.”

When the Prophet would come back from a journey, he, would say the above supplication and add: “‘We return, repent, worship and praise our Lord.” [Muslim]

*birr and taqwa: these are two comprehensive terms which individually refer to all good actions and obedience i.e. performing the commanded actions and avoiding the prohibited actions.  When combined together, birr refers to doing those actions which have been commanded and taqwa refers to avoiding those actions which have been prohibited.