Summary of the Answer:

1. Wasaa'il Ad-Da'wah (the means for propagating Da'wah) are Tawqeefiyyah (confined to the evidences), meaning, it is not allowed for anyone to introduce any means for propagating Da'wah, whether it be fundraising for a masjid or other than that from affairs related to worship. This is what the scholars mean when they say: وسائل الدعوة توقيفية! 🔺Note: 'Waseelah' is the actual method used in conveying, teaching, directing and guiding people in Deen related issues. This does not include the instruments used to communicate the means (Al-Wasaa'il Al-Aaliyyah), such as microphones; because these instruments are permissible so long as they do not oppose the Shari’ah. TV, for example, is a Waseelah Aaliyah (instrument of communication), however, due to it consisting of Tasweer, it becomes impermissible. 2. The Waseelah (means for propagating Da'wah) must be legislated and endorsed by the Shari’ah, and for this to happen it must conform to three matters: a) kitaab, b) Sunnah, & c) methodology of the Salaf; as was mentioned by Sheikhul Islam ibn Taymiyyah in 'Iqtidhaa' As-Siraat Al-Mustaqeem'. 3. Fundraising for a masjid is a Da'wah related issue. It is clearly an act of worship. Therefore, we have to refer to the evidences in order to establish whether this Waseelah is permissible or not. After referring to the evidences, we do not find this (sports tournaments) to be from the Wasaa'il endorsed by the Shari’ah. 4. Legislated Wasaa'il as it relates to fundraising for a masjid include: reminding and encouraging people to spend in the cause of Allah, cooperating upon goodness and piety, intercession... 5. The need for fundraising through such means was present during the time of the Salaf and the underlying cause was existent, but they refrained while being able to do so; this (deliberate refrainment) carries the same ruling as a verbal prohibition i.e. It's as if the Salaf are telling us: 'leave this off! Don't engage in this! It is an innovation! If it contained any good, we would have surely beaten you to it'; as mentioned by Ash-Shaafi'ee rahimahullah. So, this method is baatil (false) and an act of innovation. 6. When Al-'Allaamah Ahmad An-Najmi rahimahullah was asked about organising charity banquets and clothes bazaars as methods of fundraising, he said that this is not permissible. So what is the difference between this and organising a charity sports tournament?! In reality, these are all from the ploys utilised by the Ikhwan Al-Muslimoon to aquire people's wealth. This is why people have become weary of attending their masaajid. 7. They assume this to be in the interest of the Da'wah, but they are merely harming the Da'wah by way of this, and they are actually diverting people from the masjid and directing them towards playgrounds and towards play and games. Rather what's waajib upon them is to do the opposite. 8. It seems like the brothers intend to do good, however, as Ibn Mas'ood radhiyallahu anhu said: "Many a people seeking good fall short of the mark!" So having a good intention alone is not sufficient, we have to see if the Waseelah being used to achieve the objective is legislated, otherwise a person will fall into misguidance and innovation - even if their intention is sound.