Q 88: What does "to have Faith in the Messengers of Allah" mean?
A--- "To have Faith in the Messengers of Allah" means to have pure and absolute belief that Allah the Almighty sent down to every Ummah (community or nation) a Messenger from among them, to invite them to worship Him Alone and to renounce all that is worshipped besides Him. It means to believe that they are truthful, trustworthy, pious, divinely guided, honorable, respected, guiding and guided, supported with clear evidences and amazing miraculous signs from their Lord, and that they conveyed the whole Message they were sent with without making any change, alteration, distortion, increase or even decrease: {Then! Are the Messengers charged with anything but to convey clearly the Message?}. (An-Nahl, 35)
This also means to believe that all of them were on a clear and truthful path. To believe in them means to believe that Almighty Allah took Ibrahim (Abraham) and Muhammad (Peace be upon them) as intimate friends, Spoke to Musa (Moses), raised Idris to a lofty place, and that' Isa (Jesus)
was (no more than) a Messenger of Allah and His Word, ("Be!" - and he was) which He bestowed on Maryam (Mary) and a spirit (Ruh)(19) created by Him, and that He preferred some of them (the Messengers) to others; and others (from among them) He raised to degrees (of honor).
(19) 1Ruh-ullah: According to the early religious scholars from among the companions of the Prophet (Peace be upon him) and their students and Mujtahidun, there is a rule to distinguish between the two nouns in the genitive construction: (a) When one of the two nouns is Allah, and the other is a person or a thing, e.g. Allah's House (Bait-ullah); Allah's Messenger (Rasul-ullah); Allah's slave (' Abdullah); Allah's spirit (Ruh-ullah), the rule for the above words is that the second noun, e.g. house, messenger, slave, spirit is created by Allah and is honorable in His Sight, and similarity, Allah's spirit may be understood as the spirit of Allah, in fact it is a soul created by Allah, i.e. 'Isa (Jesus). And it was His Word: "Be!" -and he was. [i.e. 'Isa (Jesus) was created like Adam]. But when one of the two is Allah and the second is neither a person nor a thing, then it is not a created thing but is a quality of Allah e.g. Allah's Knowledge ('Ilm-ullah); Allah's Life (Hayat-ullah); Allah's Statement (Kalam-ullah); Allah's Self (Dhat-ullah). (Quoted by translator)
Reference: 200 FAQ On Muslims Belief - Shiekh Hafiz Ibn Ahmed Al Hakami