Why does the Holy Bible mention the four living creatures in both Testaments?

In both the Testaments of the Holy Bible we find visions concerning these exalted creatures who are attached to the divine throne (Isa. 6:1–7; Ex. 26:1; 36:8; Ezek. 1:1–14; Rev. 4:6–9) so that the desire to imitate these creatures by divine grace may abide in the heart of the Church.