The Messenger of Allah (sal Allahu alaihi wa sallam) said: “A slave (of Allah) may utter a word which pleases Allah, without giving it much importance, and because of that Allah will raise him to degrees (of reward): a slave (of Allah) may utter a word (carelessly) which displeases Allah, without thinking of its gravity, and because of that he will be thrown into the Fire of Hell.” [Saheeh Bukhaari]
Perhaps one such good word is “Fain Allah” in the context of the following story…
Abdullah ibn Umar (radi Allahu anhu) was once going out of Madeena with his servants. It became time to eat so the servants took the food out and everyone sat down to eat. A shepherd grazing some goats passed by and greeted them with Salaam. Ibn Umar (radi Allahu anhu) invited him to eat with them but he said, “I’m fasting.”
Ibn Umar (radi Allahu anhu) wondered aloud, “In this intense heat of summer with fiery hot winds blowing, you are fasting in the wilderness?” The shepherd replied: “I am preparing the days of my past (Ayyaam-il-Khaaliya).” The shepherd was referring to the Ayat in Surah Al-Haaqqa in which Allah (subhana wa ta’ala) says about the people in Jannah: “(It will be said to them) Eat and drink with relish, in exchange for those deeds which you did in days gone by (Ayyaam-il-Khaaliya, i.e. life in the world).” [Surah Al-Haaqqa: Ayat 24]
This Ayat means that on the Day of Resurrection it will be said to the believers: “In the world you left your desires for Allah, and you bore the difficulties of hunger and thirst, so now eat, drink and enjoy to your heart’s content and no one will stop you.” The shepherd meant that he was trying to make the days of his life in the world valuable to his Hereafter.
To test him, Ibn Umar (radi Allahu anhu) said, “We want to buy a goat. Tell us the price and take the money. We will sacrifice the goat and also give you some of the meat to open your fast with.” The shepherd replied, “These goats do not belong to me, I am a slave. They belong to my master.” Ibn Umar (radi Allahu anhu) insisted, “How will your master find out? Tell him that a wolf ate it!”
The shepherd pointed to the sky and said: “Fain Allah (Then where is Allah?)” What he meant was, “Where will Allah go while I am doing this. Allah is always watching! So how can I deceive anyone?” Ibn Umar (radi Allahu anhu) with mixed feelings of joy and amazement would keep repeating, “A shepherd says, ‘Where is Allah! Where is Allah!’”
Abdullah ibn Umar (radi Allahu anhu) returned to Madeena and went to the master of this slave. He bought from him the slave and the goats, freed the slave, and gave the goats to him as a gift. This was the condition of the shepherds of that time, that even in the middle of the jungle they worried about Allah (subhana wa ta’ala) watching them.