Deuteronomy 5:33:

Ye shall walk in all the ways which the LORD your God hath commanded you, that ye may live, and that it may be well with you, and that ye may prolong your days in the land which ye shall possess.

Notes on Deuteronomy 5:33:

Here we see another promise of healing (it isn’t well with you if you’re sick) and long life.

See also:

Some of God’s Promises Have Conditions
Is There an Appointed Time for Each Person to Die?