Clear and consimilar verses:

Allah says:

]هُوَ الَّذِيَ أَنزَلَ عَلَيْكَ الْكِتَابَ مِنْهُ آيَاتٌ مُّحْكَمَاتٌ هُنَّ أُمُّ الْكِتَاب وَأُخَرُ مُتَشَابِهَاتٌ[ (آل عمران: 7)

This means: “It is He Who has sent down to you (Muhammad SAW) the Book (this Qur'an). In it are Verses that are entirely clear, they are the foundations of the Book [and those are the Verses of Al-Ahkam (commandments, etc.), Al-Faraid (obligatory duties) and Al-Hudud (legal laws for the punishment of thieves, adulterers, etc.)]; and others not entirely clear.” (3, Al-`Imran: 7)

Repealing:

Allah says:

]مَا نَنسَخْ مِنْ آيَةٍ أَوْ نُنسِهَا نَأْتِ بِخَيْرٍ مِّنْهَا أَوْ مِثْلِهَا أَلَمْ تَعْلَمْ أَنَّ اللّهَ عَلَىَ كُلِّ شَيْءٍ قَدِيرٌ[
(البقرة: 106)

This means: “Whatever a Verse (revelation) do We abrogate or cause to be forgotten, We bring a better one or similar to it. Know you not that Allah is able to do all things?” (2, Al-Baqarah:106)

Allah says:

]يَمْحُو اللّهُ مَا يَشَاء وَيُثْبِتُ وَعِندَهُ أُمُّ الْكِتَاب[
(الرعد: 39)

This means: “Allah blots out what He wills and confirms (what He wills). And with Him is the Mother of the Book (Al-Lawh Al-Mahfuz).”
(13, Ar-Ra`d: 39)

Allah says:

]وَإِذَا بَدَّلْنَا آيَةً مَّكَانَ آيَةٍ وَاللّهُ أَعْلَمُ بِمَا يُنَزِّلُ[
(النحل: 101)

This means: “And when We change a Verse [of the Qur'an, i.e. cancel (abrogate) its order] in place of another, and Allah knows the best of what He sends down.” (16, An-Nahl: 101)