In the day of my trouble I will call upon thee - That is, I do it now; I have done it; I will do it. The language implies a habit, or a steady purpose of mind, that in all times of trouble he would make God his refuge. It was this fixed purpose - this regular habit - which was now the ground of his confidence. A man who always makes God his refuge, who has no other ground of reliance, may feel assured that God will interpose and save him.
For thou wilt answer me - This also implies a fixed and steady assurance of mind, applicable not only to this case, but to all similar cases. He had firm confidence in God at all times; an unwavering belief that God is a hearer of prayer. This is a just foundation of hope when we approach God. Compare James 1:6-7.