What is the ruling on Jama'at al-Tabligh and their activities such as "Khurooj" (going out for da'wah) and "Jawlaat" (visits to invite people)?

Jama'at al-Tabligh is a da'wah (preaching/proselytizing) group that has an impact in the field of da'wah. Scholars have differed concerning it, with some supporting it and others opposing it. It should be dealt with fairly: what conforms to the evidence is accepted, and what contradicts it is rejected. Going out for da'wah is permissible, but specifying a certain duration, such as forty days or three days, has no شرعي (Shar'i/religious legal) evidence.