Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Three kinds of people are the delegates of Allah: 1. the warrior (ghazi), 2. the one performing Hajj, 3. the one performing Umrah."
(b) It is narrated from Sayyiduna Ka'b (may Allah be pleased with him) that the delegations are of three kinds: 1. the one who fights in the path of Allah is a delegate of Allah, 2. the one who performs Hajj is also a delegate of Allah, 3. the one who performs Umrah. Whenever anyone raises his voice saying 'La ilaha illallah', or anyone saying the takbir raises his voice with the takbir, it is said: "Receive glad tidings, rejoice." Mirdas said: "With what?" He said: "Paradise."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10387