1) Not let the grass grow under one's feet. 

2) Pride may lurk under a threadbare cloak. 

3) Don’t let the grass grow under your feet. 

4) Let no grass grow under your feet. 

5) Nothing new under the sun.

6) Responsibility must be shouldered; you cannot carry it under your arms. 

7) What is there sadder under the sun than a day that is gone and notyhing done. 

8) When you want knowledge like you wanted air under water then you will get it. 

9) Nuns are under vows of poverty,(http://sentencedict.com/under.html) chastity and obedience.

10) Under normal circumstances, I would say 'yes'.

11) There's a broom cupboard under the stairs.

12) There are several amendments under consideration.

13) I shifted uneasily under his gaze.

14) We slept under the open sky.

15) The floor felt uneven under his feet.

16) The aid allocation for Pakistan was still under review.

17) Each manager had responsibility for just under 600 properties.

18) You are under pledge of secrecy.

19) They lay down under the shade of a tree.

20) Children under 14 must be accompanied by an adult.

21) We camped out under the stars.

22) The ship forged ahead under a favourable wind.

23) In hospital she'll be under observation all the time.

24) The hotel is currently under construction.

25) The doctor has injected him under the skin.

26) Willing to work under pressure with leardership quality.

27) People are still suffering under the yoke of slavery.

28) You are under no obligation to buy anything.

29) The President is under intense pressure to resign.

30) The administration of the law can never go lax where every individual sees to it that it grows not lax in his own case, or in cases which fall under his eyes.