'Sickly' in the Bible

Even so, every healthy tree bears good fruit, but the unhealthy tree bears bad fruit.

And He could not do a miracle there at all [because of their unbelief] except that He laid His hands on a few sick people and healed them.

For there is no good tree which produces bad fruit, nor, on the other hand, a bad tree which produces good fruit.

For this cause many are weak and sickly among you, and many sleep.