We learn from this beautiful hadith of our beloved ﷺ that those people who are true and complete believers can be described by specific characteristics. If one does not have those specific characteristics, it means that in those matters he/she is not completing his faith and there is a need for improvement. 

Out of the many branches of iman, 3 very important ones are addressed in this hadith and we can derive the following lessons:

1. Apart from the important rights of Allah subhanahu wa ta’ala, our treatment of other human beings and our fulfillment of their rights given by Allah are also an important part of our iman.

2. A true believer will only speak when it is good and beneficial to speak. Otherwise, he/she would remain silent. 

3. If we are not treating our neighbors well, even our non-Muslim neighbors, then we are not fulfilling that condition of faith (iman). Which means, we have a shortcoming in our iman which must be addressed. 

4. If we are not being generous and courteous to our visitors from out of town, we are also not fulfilling one of the obligatory parts of iman.