It is not a saying, nor is it a riddle, when we say that for God nothing is difficult, rather His Word is inspired by Him, given by Him, so that we can believe in Him all the time and that let there be no doubt in our hearts.
He is as real as the air we breathe every day, so it is good that we have full trust in the Lord, because He is our Good Shepherd and does not fail in the things that He does.
Let us remember that nothing is difficult for our God, creator of everything, knower of everything, because He owns all things and all things are under His feet.
25 And thou hast said unto me, O Lord God, Buy thee the field for money, and take witnesses; for the city is given into the hand of the Chaldeans.
26 Then came the word of the Lord unto Jeremiah, saying,
27 Behold, I am the Lord, the God of all flesh: is there any thing too hard for me?
Jeremiah 32:25-27 (KJV)
The previous verses tell us about a promise from God, at that time this man was desperate because other nations wanted to take possession, to enter and that is why this man was desperate.
And the word of the Lord came to that man, replying that nothing is impossible for our God, because He is Lord and owner of everything, who knows all things.
Let us not doubt the power of God, of the help of our God, He knows all things.