Abu Musa (May Allah be pleased with him) reported: Messenger of Allah (PBUH) said,

"He who The observes Al-Bardan (i.e., Fajr and 'Asr prayers) will enter Jannah."  

[Al-Bukhari and Muslim].

Commentary:

A Muslim should perform salat five times a day. Every salat has assigned time and significance. But there are some prayers that need more consideration and regularity of time than the rest. That is the reason additional merits have been attached to them, like the hadith says. Of these two is the ‘Fajr’ prayer, the performance of which is more difficult than the other prayers because it occurs at a time of rest and deep sleep. Similar is the case of 'Asr’ prayer, the performance of which is difficult too as it is the middle prayer. The hadith gives the tidings of paradise to those who take care to perform fajr and asr punctually. Hence the merit is so great that one feels entitled to do the deed.

Similarly there is another hadith that highlights the significance of fajr and asr prayer.

Abu Zuhair 'Umarah Ruwaibah (May Allah be pleased with him) reported: I heard the Messenger of Allah (PBUH) saying,

"He who performs Salat (prayers) before the rising of the sun and before its setting, will not enter the Hell."

It will be wrong to infer that one who performs these two Salat punctually will be safe from Hell merely because of his strictness in their observance, will be safe from Hell. In this Hadith, Fajr and 'Asr prayers have been particularly mentioned because of their special importance.

It is implied that one who takes special care of fajr and asr prayer and does not show any laxity in the other ones too, will be safe from hell. A Muslim who will perform all the five salah punctually but be strict in observance of fajr and asr.