i heard, there are 40 most authentic hadeeth which are common among people.some say if we learn and follow them ,we will enter jannah.Is it true? some of them are: "assalam wa qablal kalam" "naumus-subhati yamnau rizqa"

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We are not aware of the existence of 40 Prophetic narrations which are said to be the most authentic ones and that if one memorizes them and acts according to them, he will enter Paradise. However, there is much good in learning the Sunnah and acting according to it, and this is a reason for entering Paradise.

It might be that you are referring to the Prophetic narration which reads: “Whoever conveyed 40 narrations about my Sunnah to my nation, I will intercede for him on the Day of Judgment.” This narration is classified by all the scholars as Dha’eef (weak) and Al-Albaani said that it is fabricated.

Similarly, the narration “Greeting with Salaam before speaking” is not confirmed from the Prophet let alone saying that it is among the most authentic narrations, and At-Tirmithi classified it as Dha’eef and Al-Albaani classified it as fabricated.

Nonetheless, there is a narration which reads: “Whoever starts by speaking before greeting with Salaam, do not answer him” and some scholars classified it as sound.

Moreover, it is reported from ‘Uthmaan that the Prophet said: “Sleeping in the morning prevents provisions.” Al-Albaani classified it as very weak.

Allaah Knows best.