Man is not promised an endless supply of strength for him to store up. Rather, God promises to provide the necessary grace and strength for the present trials.
Men get into trouble when they begin to think too highly of their own thoughts. If they are not careful, these opinions will become the driving force in their decision making. This will mean that the word of God finds itself in competition for the seat of authority. The sad truth is that men often fail to notice within themselves this substitution of authorities. While their mouths may falsely testify of a loyal submission to the scriptures, their actions testify that their opinions are instead leading the way. The Devil works subtly because he knows how to gradually lead men astray by keeping them from noticing any abrupt changes within their hearts and outward deeds. By the time rebellion is detected, the Devil has a stronghold only broken by prayer and heartfelt submission to God.
Unfortunately, some Christians have become convinced that old age serves as a sufficient excuse for a lack of service to the Lord’s work. Granted, the field of one’s service may change, but there should always remain a willingness to serve. For instance, Moses received his initial call to deliver Israel at forty years old (Acts 7:23) but did not lead God’s people out of Egypt until he was eighty (Exodus 7:7). When he died at 120 years of age, he remarked that “his eye was not dim, nor his natural force abated” (Deuteronomy 34:7). At forty years of age, Caleb received a promise from Moses concerning the possession of land in Canaan (Joshua 14:7-9). Forty-five years later, Caleb took possession by driving out the mighty Anakims (Joshua 14:10-12). Caleb did something in his old age that many of the young men could not or would not attempt (Joshua 17:13).
