"The last Ayah revealed" or, "The last thing revealed was: They ask you about a legal verdict. Say: 'Allah directs (thus) regarding Al-Kalalah (4:176).'"
Jami` at-Tirmidhi Book 47, Hadith 93
← Previous Hadith "Sawdah feared that the Prophet (ﷺ) was going to divorce her, so she said: 'Do not divorce me, but keep me and give my day to 'Aishah.' So he (ﷺ) did so, and the following was revealed: Then there is no sin on them both if they make terms of peace between themselves, and making peace is better (4:128). So whatever they agree to make peace in something then it is permissible."

Jami` at-Tirmidhi Book 47, Hadith 92 Next Hadith → "A man came to the Messenger of Allah (ﷺ) and said: 'O Messenger of Allah! They ask you about a legal verdict. Say: "Allah directs (thus) regarding Al-Kalalah (4:176)." So the Prophet (ﷺ) said to him: "You should be sufficed with the Ayah of summer."

(Meaning this Ayah, while in An-Nisa number 12, is mention of the topic, and it was revealed in the winter, this Ayah, revealed in the summer - the last revealed about it - explains it)

Jami` at-Tirmidhi Book 47, Hadith 94