'Straining' in the Bible

'Blind guides! who are straining out the gnat, and the camel are swallowing.

He saw that his disciples were straining at the oars, because the wind was against them. Shortly before dawn he came to them, walking on the sea. He intended to go up right beside them,

Brothers, I do not consider myself to have embraced it yet. But this one thing I do: Forgetting what lies behind and straining forward to what lies ahead,