1) Imagination is the source of creation. 

2) Economy is in itself a source of great revenue. 

3) Fame like a river is narrowest at its source and broadest afar off. 

4) Friendship is both a source of pleasure and a component of good health. 

5) Where is the source of the Nile?

6) Where is the source of the Rhine?

7) Chopping boards can be a source of cross-contamination.

8) We couldn't locate the source of the radio signal.

9) The tiny window was the only source of light.

10) Fruit is a convenient source of vitamins and energy.

11) We're interested in the source of these fictitious rumours.

12) We must trace the source of these noxious gases.

13) Spinach is a valuable source of iron.

14) The source of the gunshots still remains a mystery.

15) Success in sport is a source of national pride.

16) Tax is deducted at source.

17) Bad food is a source of illness.

18) We must trace the source of these noxious.

19) Liver is a particularly rich source of dietary iron.

20) What is their main source of income?

21) Peaches are a good source of fibre.

22) Oranges are a good source of vitamin C.

23) I verified the source from which I had that information.

24) He wanted to have a source of income after his retirement; until then,(http://sentencedict.com/source.html) he wouldn't require additional money.

25) Dreams can be a rich source of inspiration for an artist.

26) The heavy traffic is a constant source of irritation .

27) It is conflict and not unquestioning agreement that deeps freedom alive. In a free country there will always be coflicting ideas, and this is a source of strength. 

28) Money is a singular thing, It ranks with love as man's greatest source of joy. And with death as his greatest source of anxiety. 

29) Wordsworth found inspiration in/drew inspiration from the Lake District scenery. It was a great source of inspiration to him.

30) The doctor opened up his stomach to get at the source of the trouble.