وَإِذْ أَخَذَ اللّهُ مِيثَاقَ النَّبِيِّيْنَ لَمَا آتَيْتُكُم مِّن كِتَابٍ وَحِكْمَةٍ ثُمَّ جَاءكُمْ رَسُولٌ مُّصَدِّقٌ لِّمَا مَعَكُمْ لَتُؤْمِنُنَّ بِهِ وَلَتَنصُرُنَّهُ قَالَ أَأَقْرَرْتُمْ وَأَخَذْتُمْ عَلَى ذَلِكُمْ إِصْرِي قَالُواْ أَقْرَرْنَا قَالَ فَاشْهَدُواْ وَأَنَاْ مَعَكُم مِّنَ الشَّاهِدِينَ

What the Bahais say:
This verse refers to Bahaullah. Allah took the covenant from the prophets regarding the prophethood of Bahaullah.

What is the basis of this interpretation:
It is certainly not based in Quran and Sunnah. This is one of the many verses referring to Prophet Mohammed (pbuh) that according to the Bahais refers to Bahaullah.

What the Muslims say
This verse refers to Prophet Mohammed (pbuh).

A. Interpretation of this verse from Ahle Sunnah sources
In Al Durrul Mansoor, the author - Jalaluddin Suyuti has brought more than a dozen traditions related to this verse none of which refer to Bahaullah. On the contrary they refer to Prophet Mohammed (pbuh). For illustrative purpose I have mentioned two of these traditions.

Ibne Jarir narrates from Ali bin Abi Talib: 'Allah has not raised a Prophet from Adam but He has extracted a covenant from each of them regarding Mohammed (pbuh) that they believe in him and help him. Then Ali b. Abi Talib recited this verse: ''Behold! Allah took the covenant of the prophets, saying: "I give you a Book and Wisdom; then comes to you an apostle, confirming what is with you; do ye believe in him and render him help.'
(Ref: Al Durrul Mansoor, volume 2, page 44)

Ibne Jarir and Ibne Abi Hatim narrate from Sodayy regarding the verse (Surah Ale Imran, verse 81): Allah has not raised a single prophet but He has extracted a covenant from them that they believe in Mohammed and help him.
(Al Durrul Mansoor, volume 2, page 44)

B. Interpretation of this verse from Shia sources
1. According to traditions in Tafsire' Ali bin Ibrahim Qummi (volume 1 page 114), a leading Shiite interpreter of the Quran, this verse refers to Prophet Mohammed (pbuh).

2. According to traditions reported by Mohammed bin Hasan Saffaar, a leading Shiite narrator of traditions and author of Basairud Darajaat (page 25), this verse refers to Prophet Mohammed (pbuh).

It is worth noting that both Ali bin Ibrahim Qummi and Mohammed bin Hasan Saffaar are among the most notable companions of the Holy Imams. Therefore their reports assume even more significance, certainly a lot more than what the Bahais can lay claim to, having arrived more than a thousand years later and without having encountered a single infallible Prophet or Imam.