on the authority of abu hurairah (radiallaahu anhu) that the messenger of allaah (sallallaahu alayhi wa sallam) said :

it was related by al-bukhaaree and muslim.

explanation of hadeeth number 15

his (sallallaahu alayhi wa sallam) statement "let him who believes in allaah and the last day" means the one who believes with the complete eemaan that will save him from the punishment of allaah, and will attain for him the pleasure of allaah; then for such a person, "let him speak good, or keep silent", because the one who believes in allaah and does not fulfill everything that his eemaan entails [ie. he falls into sin] then he fears his threat [of punishment] and he hopes in his reward, and he strives in performing what he has been commanded with, and in leaving that which he has been forbidden from. and the most important of what is upon him from this is being careful about his tongue and limbs, which are under his control, and which he will be asked about on the day of standing, as allaah ta'aalaa has said : "verily! the hearing, and the sight, and the heart, of each of those you will be questioned (by allaah)" [al-israa', 36]. and allaah ta'aalaa has said : "not a word does he (or she) utter, but there is a watcher by him ready (to record it)" [qaaf, 18].

and the sins of the tongue are numerous, and because of this the prophet sallallaahu alayhi wa sallam said : "and what is it that throws the people into the hellfire upon their noses, except what their tongues have harvested" and he (sallallaahu alayhi wa sallam) has said : "everything that the son of aadam speaks will be a proof against him, except the dhikr of allaah and his ordering the good and forbidding the evil". so whosoever understands this, and protects the rights of his eemaan, then he will fear allaah and have taqwaa of him with regards to his tongue, and he will not speak except with good, or will remain silent.

some of the 'ulamaa have mentioned that all of the good manners can be derived from four hadeeth, and they mentioned amongst them this hadeeth. and some them have said regarding the meaning of this hadeeth that if a person wishes to say something, then if that speech is good, and will surely be rewarded for, then let him say it. and if not, then let him keep silent - whether it is apparent that the speech is haraam (forbidden) or makrooh (disliked) or even mubaah (permissible). so from this it is said that the permissible speech is to be left and avoided, and rather it is preferred to keep silent in such situations, out of fear that it may turn into something which is haraam or makrooh; and it is seen that this happens a great deal, and thus allaah has said : "not a word does he (or she) utter, but there is a watcher by him ready (to record it)" [qaaf, 18].

however, the 'ulamaa have differed over whether everything that a person says is written down by the recording angels, including that which is considered mubaah (permissible), or if it is only those things for which he may be rewarded or punished. and ibn 'abbaas (radiallaahu anhu) and others have adopted this second opinion, and so in this case the aayah mentioned above would have its meaning restricted to those words or statements for which there is some kind of recompense - good or bad.

and his (sallallaahu alayhi wa sallam) statement "let him be generous to his neighbour" and "let him be generous to his guest" contains instruction on the rights of the neighbours and guests, and on doing good to them and encouragement upon protecting the limbs from doing harm to them, and also allaah ta'aalaa has advised us in his noble book with ihsaan (good behaviour, kindness, good treatment) towards the neighbours. and the prophet sallallaahu alayhi wa sallam has said : "jibreel - alayhi as-salaam - did not cease to advise me regarding the rights of the neighbour, until i began to think that they would also receive a part of the inheritance".

and hospitality is from islaam, and from the character of the prophets and the pious. and some of the scholars have made it obligatory, though the majority consider it to be from the noble, recommended traits of character. and the author of "al-ifsaah" has said regarding this hadeeth :
"it should be believed that hospitality to the guest is a means of attaining nearness to allaah, and that it is a form of worship of the lord, and that this worship is not decreased if the guest is a wealthy person (rather than a poor man), nor is it affected if one presents for ones guest simple things from what one posseses. rather, the correct hospitality is achieved by keeping a smiling countenace for ones guest, and beautifying ones conversation with him, and the pillar of hospitality is preparing a meal for the guest; and so one should be eager to prepare for him from what allaah has provided and made easy, without causing oneself undue difficulty."

he then mentioned some other points on hospitality, before saying :
"and as for his (sallallaahu alayhi wa sallam) statement 'let him speak good or keep silent', then this indicates that the good speech is better than keeping silent, and that silence is better than evil speech, and this is because the form of the prophet's (sallallaahu alayhi wa sallam) statement contains a command. and from the good speech is conveying knowledge from allaah 'azza wa jall and his messenger sallallaahu alayhi wa sallam, and teaching the muslims, and commanding the good, and forbidding the evil, and reconciling the differences between people, and speaking well to the people, and from amongst the best of speech is the statement of truth, for the one who truly fears and hopes for the recompense."

summary :

• that one should only speak what is good and true
• that one must not under any circumstances speak evil or use filthy language
• that one should be kind and generous to ones neighbour
• that one should treat ones guest well
• that if one is a true muslim then one would do the above, else ones [true] belief in allaah and the last day is in question