This hadith has been narrated from Jarir on the authority of A'mash with the same chain of transmitters and he said : When (fasting) in Ramadan was (made) obligatory, he abandoned it (the practice of observing fast on Ashura).
The hadith also teaches us to be mindful of our religious obligations and prioritize them over other practices which are not mandatory for us to do. We should always strive to fulfill our religious duties first before anything else as this will bring us closer to Allah SWT and help us attain His blessings in this world and hereafter.