Or do they, perchance, think that We do not hear their hidden thoughts and their secret confabulations?56
Yea, indeed, [We do,] and Our heavenly forces57
are with them, recording [all].
This is most probably an allusion to the centuries-long subtle Christian controversies on the question as to whether or not Jesus was "the son of God" and, hence, divine. These controversies were often influenced by a subconscious leaning of some of the early Christian thinkers towards ancient, mostly Mithraistic, cults and concepts which were in the beginning strongly opposed by unitarian theologians, foremost among them Arius, Patriarch of Alexandria (about 280-336 C.E.). However, at the politically-motivated Council of Nicaea (325 C.E.), the Arian views - which until then had been shared by the overwhelming majority of articulate Christians - were condemned as "heretical", and the doctrine of Christ's divinity was officially formulated in the so-called Nicene Creed as the basis of Christian beliefs. (See also note  below).
Lit., "Our messengers", i.e., angels.