When My servants question thee concerning Me, then surely I am nigh. I answer the prayer of the suppliant when he crieth - Quraan 2:186 (5)

"Our Lord! Cause not our hearts to stray after Thou hast guided us, and bestow upon us mercy from Thy Presence. Lo! Thou, only Thou, art the Bestower.

Our Lord! Lo! it is Thou Who gatherest mankind together to a Day of which there is no doubt. Lo! Allah faileth not to keep the tryst. " Quraan 3:8-9

رَبَّنَا لاَ تُزِغْ قُلُوبَنَا بَعْدَ إِذْ هَدَيْتَنَا وَهَبْ لَنَا مِن لَّدُنكَ رَحْمَةً إِنَّكَ أَنتَ الْوَهَّابُ

رَبَّنَا إِنَّكَ جَامِعُ النَّاسِ لِيَوْمٍ لاَّ رَيْبَ فِيهِ إِنَّ اللَّهَ لاَ يُخْلِفُ الْمِيعَادَ

آل عمران : ٨-٩

This is another way the Almighty like to be entreated. To ask Him to help us maintain the straight path. However, the supplication has a confusing statement that seems contradictory to the purpose He created us for!

"Cause not our hearts to stray after Thou hast guided us"

If Allah created us to test us why would He cause our hearts to stray or not to?! If He does so then it's unfair that He will punish us if we committed sins because He strayed our hearts! Neither we will deserve the reward for whatever good we do because He didn't stray our hearts!

The answer is in the previous post of this series. I don't think Allah will cause our hearts to be strayed or not, even though He is totally capable to do so! It would be unjust for Him to do so; only the weak practices injustice while He has the ultimate power, thus He will never be unjust. However, He can test us with difficult (yet sill can be passed successfully) trials that we may fail in, consequently that failure will cause our hearts to be strayed but it's us who are liable about our failures not Him. Thus, the supplication is about asking Him not put us through difficult tests that we may fail in.