All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The mere emission of Mathy does not require performing Wudhoo’, but one must perform Wudhoo’ on account of Mathy when one intends to perform the prayer according to the view of most scholars. In this regard, it is like urine. However, some scholars said that it is necessary to perform Wudhoo’ as soon as it is emitted even if one does not intend to perform the prayer.
Ibn Hajar said in his commentary on the Hadeeth narrated by ‘Ali about Mathy:
"It was evidenced by the saying of the Prophet, sallallaahu ‘alayhi wa sallam: 'Perform Wudhoo’' that Ghusl is not obligatory on account of the emission of Mathy. He explicitly mentioned this in a Hadeeth reported by Abu Daawood and others, and it is a consensus. And this Hadeeth is also evidence that the command of Wudhoo’ for Mathy is like the command of Wudhoo’ for urine, as the author cited as evidence above in the Chapter entitled "Those who do not hold Wudhoo’ to be necessary without discharge from the two passageways". Also, At-Tahaawi reported from a group of scholars that Wudhoo’ is required as soon as Mathy is emitted, and he refuted their statement with what he reported on the authority of Abdur-Rahmaan ibn Abi Layla from ‘Ali who said: the Prophet, sallallaahu ‘alayhi wa sallam, was asked about Mathy and he replied: 'Wudhoo’ is required for it, and Ghusl is required for semen.' Therefore, it is known from this that the ruling of Mathy is the same ruling as that of urine and other invalidators of Wudhoo’, and not that Wudhoo’ is required as soon as one has a discharge of Mathy."
Al-Kashmeeri said in his Commentary on the Sunan of At-Tirmithi: "Most of the jurists are of the view that performing Wudhoo’ on account of Mathy is one of the rules of the prayer, so it is obligatory to do it before performing prayer. On the other hand, it is attributed to (Imaam) Ahmad that it is among the rules associated with Mathy; and it is the apparent (view)." [End of quote]
Allaah Knows best.