The Quran

وَإِذ أَخَذَ اللَّهُ ميثاقَ النَّبِيّينَ لَما آتَيتُكُم مِن كِتابٍ وَحِكمَةٍ ثُمَّ جاءَكُم رَسولٌ مُصَدِّقٌ لِما مَعَكُم لَتُؤمِنُنَّ بِهِ وَلَتَنصُرُنَّهُ ۚ قالَ أَأَقرَرتُم وَأَخَذتُم عَلىٰ ذٰلِكُم إِصري ۖ قالوا أَقرَرنا ۚ قالَ فَاشهَدوا وَأَنا مَعَكُم مِنَ الشّاهِدينَ

Muhammad Asad

AND, LO, God accepted, through the prophets, this solemn pledge [from the followers of earlier revelation]:¹ "If, after all the revelation and the wisdom which I have vouchsafed unto you, there comes to you an apostle confirming the truth already in your possession, you must believe in him and succour him. Do you" - said He - "acknowledge and accept My bond on this condition?" They answered: "We do acknowledge it." Said He: "Then bear witness [thereto], and I shall be your witness.²

Lit., "the solemn pledge of the prophets". Zamakhshari holds that what is meant here is a pledge taken from the community as a whole: a pledge consisting in their acceptance of the messages conveyed through the prophets.
Lit., "and I am with you among the witnesses".