Nehemiah 9:16

But they and our fathers dealt proudly, and hardened their necks.

Hardened by sin

Dr. Manton says: “As a delicate constitution is more capable of pain than a robust and stubborn one, and the tender flesh of a child will sooner feel the lash than the thick skin of a slave, so the children of God, having a more serious apprehension of things, and a more tender spirit, soonest feel the burden of their Father’s displeasure, and do more lay it to heart than careless and stupid spirits, who laugh at their cross, or drink away their sorrows.” Tenderness of heart is thus an attribute of the child of God, and a very precious attribute, too. Hard-hearted men are not men after God’s own heart. In proportion as feeling declines, life has declined. Spiritual men are sensitive men. Ossification of the heart is a fatal disease. Declensions in grace are a searing of the soul. When water is warmed by the summer sun, the smallest stone sinks into it; when it is frozen in the northern blast, a huge block will be borne up upon the surface of it, and will never penetrate to its depths. So, when the soul grows cold with distance from God, it will sustain an enormous weight of sin; but when grace returns, and the soul is in a fight spiritual condition, an ounce of sin will be more than the soul can bear. Oh, for more of this holy sensitiveness! (C. H. Spurgeon.)