The Messenger of Allah, sallallahu 'alayhi wa sallam (may Allah's peace and blessing be upon him), said, "Taqwa is here," and he pointed to his chest. [Muslim (16/120, 121) in al-Birr, at-Tirmidhi (8/115) in al-Birr and Ahmad (2/277)]
'Umar ibn 'Abdul-'Aziz, rahimahullah (may Allah have mercy upon him), used to say, "None can reach the station of taqwa until he possesses neither action nor words that can be exposed to his embarrassment either in this world or the Hereafter." He was once asked, "When does the worshipper reach the peak of taqwa?" He replied, "If he put all his thoughts and desires in his heart on a plate and then wandered around in the market, he should not feel ashamed of anything there." He would frequently say, "The sign of muttaqi (pious person) is to bridle oneself from speaking just like one in ihram bridles himself from speaking.
Abu Darda, radiallahu 'anhu (may Allah be pleased with him), said, "From the completion of taqwa is that the slaves fears from his Lord even with regards to things the weight of an atom."
Abu Hurayrah, radiallahu 'anhu, was asked about taqwa. He said, "It is a road full of thorns. One who walks it needs to have extreme patience."
Sufyan ath-Thawri rahimahullah said, "We met a people who loved it when it was said to them - Fear Allah the Most High. Today you find that people only become annoyed at this."
A person asked Fudhayl ibn 'Iyad rahimahullah, "Which country would you like me to live in?" Fudhayl replied, "There is no connection between you and any nation. The best country for you is the country which helps you to acquire taqwa."