'Old' in the Bible

Saul’s son Ish-bosheth was 40 years old when he began his reign over Israel; he ruled for two years. The house of Judah, however, followed David.

Saul’s son Jonathan had a son whose feet were crippled. He was five years old when the report about Saul and Jonathan came from Jezreel. The one who had nursed him picked him up and fled, but as she was hurrying to flee, he fell and became lame. His name was Mephibosheth.

David was 30 years old when he began his reign; he reigned 40 years.

Barzillai was a very old man—80 years old—and since he was a very wealthy man, he had provided for the needs of the king while he stayed in Mahanaim.

I’m now 80 years old. Can I discern what is pleasant and what is not? Can your servant taste what he eats or drinks? Can I still hear the voice of male and female singers? Why should your servant be an added burden to my lord the king?