Ibn Majah

Lexical Explanation:
«رُعَافٌ» "Ra" has a dammah and "Ayn" is lightened. The blood that comes out from the nose is called "ru‘af," i.e., nosebleed (naqsir).
«قَلْسٌ» The "qaf" has a fathah and the "lam" is silent. Any food or drink that exits from the stomach through the mouth.
«لِيَبْن» Its "lam" is the imperative lam. The explanation is that a person began the prayer, had performed one, two, or more units (rak‘ahs), and then lost his ablution (wudu). Now, after performing a new ablution, if he returns and resumes the prayer without any kind of conversation, he should count what he had already performed and complete the remaining units, then end with salam. The units performed before losing ablution will not be wasted, and he will not have to repeat the entire prayer from the beginning.
«وَهُوَ فِي ذٰلِكَ لَا يَتَكَلَّمُ» "And during this, he should not engage in any kind of conversation." This is a circumstantial clause indicating a condition. Its meaning is that when his ablution is broken, the condition for resumption (bina) is that from the time he performs ablution and returns to join the prayer, he must not engage in any conversation. If he does converse, he cannot resume (bina); he must perform the entire prayer anew. However, this is not correct, as will be detailed further.

Benefits and Issues:
➊ In the case of the emission of madhiy (pre-seminal fluid), the jurists are unanimously agreed that ablution (wudu) is nullified. However, regarding vomiting, the exit of any food or drink from the stomach through the mouth, and the flow of blood from the nose (i.e., nosebleed), one group holds that ablution is nullified, while another group holds that it is not.
➋ Similarly, there is a difference of opinion regarding resumption (bina). Imam Malik and Imam Abu Hanifah rahimahumullah both hold the view of resumption, while Imam Shafi‘i rahimahullah does not. The evidence for the first group is this very hadith, which Imam Ahmad rahimahullah has declared weak. Imam Shafi‘i rahimahullah says: When the worshipper loses ablution, the prayer no longer remains. When the prayer itself does not remain, then upon what will resumption be based?
➌ Likewise, there is a difference of opinion among the Imams regarding the nullification of ablution due to nosebleed. Imam Abu Hanifah rahimahullah says that both vomiting and nosebleed nullify ablution. In contrast, Imam Malik and Imam Shafi‘i rahimahumallah say that nosebleed and the like do not nullify ablution.
➍ Among the Companions radi Allahu anhum, Abdullah ibn Umar, Jabir ibn Yazid, Abdullah ibn Abbas, Ibn Abi Awfa, and Abu Hurairah radi Allahu anhum, and among the Followers (Tabi‘in), Sa‘id ibn al-Musayyib, Mak‘hul, and Rabi‘ah rahimahumullah and others also hold the view that ablution is not nullified by vomiting or nosebleed.
➎ The correct view is that this hadith is weak and mursal, and it also contradicts authentic ahadith, so it cannot be used as evidence.