Here Allah commands His servants to have Taqwa of Him, worshipping Him as if they can see Him, and to
(speak (always) the truth.) meaning, to speak in a straightforward manner, with no crookedness or distortion. He promises them that if they do that, He will reward them by making their deeds righteous, i.e., enabling them to do righteous deeds, and He will forgive them their past sins. With regard to whatever sins they may commit in the future, He will inspire them to repent from them. Then He says:
(And whosoever obeys Allah and His Messenger, he has indeed achieved a great victory.) meaning, he will be saved from the fire of Hell and will enjoy everlasting delights (in Paradise).