It means that Allah (SWT) sent the Messengers like Musa (Moses), Isa (Jesus), Ibrahim (Abraham), Nuh (Noah), etc. (peace be upon them all) and sent down the books like the Torah, Injeel (Gospel), Zaboor (Psalms), etc. to call the people to worship Allah (SWT) Alone, associating nothing with Him.
Kii u horreeyey ayaa iyaga kor mari doona sida Hillaaca soo socda sida dabayl oo kale ayay soo socda sida shimbir, oo ku xiga sida xawaaraha ah geel ah, halka Nabigeena waa on waxay Baryaan Bridge ka, 'O Allah, kaalmeeammaanka, wuxuuna siin cid nabadgelyada! '