Poison in the Cup

Today's office hymn included the portions:
What God ordains is always good.
His loving thought attends me.
No poison can be in the cup
That my Physician sends me.
and later
What God ordains is always good.
Though I the cup am drinking
Which savors now of bitterness
I take it without shrinking.

Poison usually tastes bitter. It's a protection for us: the natural reaction to the bitter taste is to spit it out before the poison gets into you.

However, medicine usually tastes bitter too. (Or at least, it did in the old days before we came up with all the chemical concoctions we have for medicine now.)

So if I am drinking the cup which savors of bitterness, I will be inclined to think that it's poisonous. But it could be medicine from the Physician. Hard to tell, based just on the experience of bitter taste. According to the hymnist, what God gives will be good, even if it appears to my senses to be dangerously poisonous and distasteful.