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. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Allaah Says (which means): {O you who have believed, when you go forth [to fight] in the cause of Allah, investigate;…}[Quran 4:94]. Investigate is a translation of the meaning of the Arabic word 'Fatabayyanu' but it is reported that this very word in the same verse is also read instead as 'Fatathabbatu'. Both ways of reading the verse, i.e. using the first or second word are correct and authentic from the Prophet . Reading the verse using the first word [in the Arabic language] is the way the majority of reciters of the Quran read it, and the second way of reading it (i.e. using the second word) is the way Hamzah read it, as the questioner mentioned.
Allaah Knows best.