Hadith no. 178 is a repeat. Read it here.
Abrogation is like putting an end to something. A few verses (ayaat) of the Quran were abrogated and some Ahadith as well. It was due to different needs of the Muslims in different situations. Remember, the only one having the power/ability to abrogate a verse/order is Allah. No human being has done it/can do it. Read more about it here. An example will be found in today’s Hadith.
Narrated Zaid bin Khalid:
I asked ‘Uthman bin ‘Affan about a person who engaged in intercourse but did no discharge. ‘Uthman replied, “He should perform ablution like the one for ar ordinary prayer but he must wash his penis.” ‘Uthman added, “I heard it from Allah’s Apostle.” I asked ‘Ali Az-Zubair, Talha and Ubai bin Ka’b about it and they, too, gave the same reply. (This order was cancelled later on and taking a bath became necessary for such cases).
So in the beginning, only ablution (wudu) was required after the described intercourse. But later on, the hukm (order) changed, and ghusl (bath) became compulsory. Who did it? Allah!
There’s a lot of discussion regarding how’s and why’s on this subject, but let’s not touch that topic..