Surah Al-Baqarah (The Cow), Verse 91

وَاِذَا قِیْلَ لَهُمْ اٰمِنُوْا بِمَاۤ اَنْزَلَ اللّٰهُ قَالُوْا نُؤْمِنُ بِمَاۤ اُنْزِلَ عَلَیْنَا وَیَكْفُرُوْنَ بِمَا وَرَآءَهٗ وَهُوَ الْحَقُّ مُصَدِّقًا لِّمَا مَعَهُمْ قُلْ فَلِمَ تَقْتُلُوْنَ اَنْۢبِیَآءَ اللّٰهِ مِنْ قَبْلُ اِنْ كُنْتُمْ مُّؤْمِنِیْنَ ۟

Wa izaa qeela lahum aaminoo bimaaa anzalal laahu qaaloo nu'minu bimaaa unzila 'alainaa wa yakfuroona bimaa waraaa'ahoo wa huwal haqqu musaddiqal limaa ma'ahum; qul falima taqtuloona Ambiyaaa'al laahi min qablu in kuntum mu'mineen

“When it is said to them, "Believe in what Allah Hath sent down, "they say, "We believe in what was sent down to us:" yet they reject all besides, even if it be Truth confirming what is with them. Say: "Why then have ye slain the prophets of Allah in times gone by, if ye did indeed believe?"”

Quran 2:91 (Yusuf Ali Translation)