  Recent neutron scattering measurements indicate that NaFe$_{1-x}$Cu$_{x}$As
forms an antiferromagnetic stripe phase near $x\approx 0.5$ in a Mott
insulating state. This copper concentration is well in excess of that required
for superconductivity, $x < 0.04$. We have investigated the development of
magnetism in this compound using $^{23}$Na nuclear magnetic resonance (NMR)
spectra and spin-lattice relaxation measurements performed on single crystals
($x$ = 0.13, 0.18, 0.24, and 0.39). We find multiple inequivalent Na sites,
each of which is associated with a different number of nearest neighbor Fe
sites occupied by a Cu dopant. We show that the distribution of Cu substituted
for Fe is random in-plane for low concentrations ($x = 0.13$ and 0.18), but
deviates from this with increasing Cu doping. As is characteristic of many
pnictide compounds, there is a spin pseudo gap that increases in magnitude with
dopant concentration. This is correlated with a corresponding increase in
orbital NMR frequency shift indicating a change in valence from Cu$^{2+}$ to a
Cu$^{1+}$ state as $x$ exceeds 0.18, concomitant with the change of Fe$^{2+}$
to Fe$^{3+}$ resulting in the formation of magnetic clusters. However, for
$x\leq 0.39$ there is no evidence of long-range static magnetic order.
