I do not know whose statement it is:" It is the last word of the Messenger of Allah (ﷺ) which is accepted as (final as it abrogates the previous ones)."
A hadlth like this has been transmitted on the authority of Ibn Shibab who said that they (the Compnions of the Holy Prophet) followed the latest of his commands and looked upon it as one abrogating (the previous ones) and the most firm.
وَحَدَّثَنَا أَبُو كُرَيْبٍ، حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ عَبْدِ الْكَرِيمِ، عَنْ طَاوُسٍ، عَنِ ابْنِ، عَبَّاسٍ - رضى الله عنهما - قَالَ لاَ تَعِبْ عَلَى مَنْ صَامَ وَلاَ عَلَى مَنْ أَفْطَرَ قَدْ صَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم فِي السَّفَرِ وَأَفْطَرَ .
Do not condemn one who observes fast, or one who does not observe (in a journey). for the Messenger of Allah (ﷺ) observed fast in a journey or he did not observe it (too).
It was said to him (to the Holy Prophet): There are people to whom fasting has become unbearable and they are waiting how you do. He (the Holy Prophet) then called for a cup of water when it was afternoon. The rest of the hadith is the same.
What is the matter with him? They said: He is a person observing fast. Whereupon the Messenger of Allah (ﷺ) said: It is no righteousness that you fast on journey.
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ، قَالَ سَمِعْتُ مُحَمَّدَ بْنَ عَمْرِو بْنِ الْحَسَنِ، يُحَدِّثُ أَنَّهُ سَمِعَ جَابِرَ بْنَ عَبْدِ اللَّهِ، - رضى الله عنهما - يَقُولُ رَأَى رَسُولُ اللَّهِ صلى الله عليه وسلم رَجُلاً بِمِثْلِهِ .
'Amr b. al-Hasan is reported to have said that he heard Jabir b. 'Abdullah (Allah be pleased with both of them) as saying that the Messenger of Allah (ﷺ) saw a man. The rest of the hadith is the same as mentioned above.
" Take advantage of the concession of Allah Who Wanted it to you." When he (one of the narrators) asked him (the other one, Yabya b. Abi Kathar) he did not retain it in his mind.