As a fountain cannot produce both sweet water and bitter at the same time, so God cannot be the source of illness and misfortune. See James 3

Through the fountain of good thoughts, God provides only what can bless us.

Here’s what Jesus said. “Doth a fountain send forth at the same place sweet water and bitter? Can the fig tree, my brethren, bear olive berries? either a vine, figs? so can no fountain both yield salt water and fresh.”
(James 3:11, 12)

Trust in the Lord, and do good; so shalt thou dwell in the land, and verily thou shalt be fed.
(Psalms 37:3)

We cannot have a good thought without it having a good effect.