אלהי מסכה לא תעשה… חג המצות תשמור (כי תשא לד:יז-יח)

A Yid once came to the holy Apter Rav zt”l and lamented about his son who became an epikorus – an atheist – and wanted to leave the fold.  He asked the Rebbe to daven for his son to return to the path of Yiddishkeit – Judaism.  The Apter Rav told him: “If you know that your son did not eat chometz during Pesach when he was already off the trodden path, then there is still hope. However, if he did eat chometz, then we cannot help him”.

This is alluded to in the two adjoining pessukim in our parsha: אלהי מסכה לא תעשה… חג המצות תשמור – one is dependent on the other.