Answered by Shaykh Ilyas Patel
In the tashahuhd of the prayer, after the at-tahiyat o lillahi….wa ala ibadillah his saliheen…we say the shahada…are we supposed to say: “as hadu alla ilaha il Allah wa ash hadu ana Muhammadan abduhu wa rasoolohu”….. (or is it rasuluh?) or do we say: “as hadu alla ilaha il Allah wahdahu la shareeka la, wa ash hadu ana Muhammadan abduhu wa rasoolohu”?

In the Name of Allah, the Beneficent, the Merciful, and all blessings and peace upon our master Muhammad, his Folk, Companions and those who follow their noble way,
The preferred wording of the tashahhud in the Hanafi school is :
Al-Tahiyatu lillahi wassalawatu wa-tayibatu as salamu alayka ayyuhan nabiyu warahmatllahi wa barakatuh As salmualayna wala ibadillahi salihin as hadu alla ilaha il Allah wa ash hadu ana Muhammadan abduhu wa rasooloh. [Shurunbulali, Nur ul’l-Idah pg 75]
One will end with reading RASULUH and not rasuluhu. This is because one is ending a sentence.
– Ilyas Patel