Musar על ברכות 125:22

Chazal have also said (Berachoth 63a): "All who are lax in Torah study will lack the strength to withstand a day of affliction, viz. (Mishlei 24:10): 'If you grow lax, in a day of affliction your strength will be straitened.'" And we find in the holy Zohar on this verse: