1.  Allah Subhanahuthala insisted every Muslim to invoke this supplication several times a day. What is that supplication?
                                         
السلام عليكم ورحمة الله وبركاتة 

بِسْمِ ٱللَّٰهِ ٱلرَّحْمَٰنِٱلرَّحِيمِ

Answer:

○ صِرَٰطَ ٱلَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ ٱلْمَغْضُوبِ عَلَيْهِمْ وَلَا ٱلضَّآلِّينَ ○ ٱهْدِنَا ٱلصِّرَٰطَ ٱلْمُسْتَقِيمَ

Guide us to the straight path - The path of those upon whom You have bestowed favor, not of those who have earned [Your] anger or of those who are astray. [Al Fathiha, the last two ayaath].

When we recite this particular supplication, Allah Subhanahuthala responds to it. He has told, this in a hadheesae-Qudsi, ‘This (part of surah) is for My slave, and My slave will have what he requests.’ (Muslim, 395).

There is only one path of truth and that is the "path of Allah". Allah (Azza wa jall) says, “This is My path which is straight, so follow it. Do not follow other ways, for they cause you to deviate from His way. This is what He has instructed you to do, so that you will have taqwā (piety)” (6:153).

There are three categories of people, who follow this divine guidance:

1. The Blessed ones – [أَنْعَمْتَ عَلَيْهِمْ]
2. Those who incurred anger [غَيْرِ الْمَغْضُوْبِ].
3. The misguided [وَلَا الضَّآلِّيْنَ]

The blessed people stated in this ayah are described in Surah al-Nisa. Allah (Azza wa jall) says, “Whoever obeys Allah and the Messenger will be with those whom Allah has blessed: the Prophets and the Ṣiddiqin, the martyrs and the righteous. What excellent company such people are!” (4:69).

Those who incurred anger are those who had the knowledge but did not act upon it, deliberately rejecting the truth and inventing their own falsehood. And they also  make others to follow their path.

The misguided ones are those who lacked the knowledge and yet willingly go astray themselves.

Narrated 'Adiyy bin Hatim: that the Prophet (SAW) said: "The Jews are those who Allah is wrath with, and the Christians have strayed." [Jami` at-Tirmidhi, 2954]

God’s wrath will also be upon:

● the hypocrites;
● the polytheists; 
● those with evil assumption about God;
● those who disbelieve in the signs of Allah;
● those who killed the prophets;
● the people of the book  who were hiding the truth;
● those who turned away from struggling in the path of  Allah;
● the believers turning to disbelief and
● those accepting the friendship and leadership of enemies of God.


We seek this supplication specifically to Allah (Azza wa jall):

★ to avoid the constant whispering of accursed Shaithan who deviate us from the straight path;
★ to safeguard the  superior guidance and knowledge given to us;
★ to prevent us following the fabricated guidance and transgression;
★ to place us in the company of His best creation;
★ to direct us to have lofty aspirations; and
★ to strive towards the best.

Hence we should always thank Allah (Azza wa jall) for the blessings of iman, guidance and born as Muslims.

These two ayaath also remind us to be optimistic, ambitious, extremely hopeful and always consistant while we are making any dua.

الحمدلله