رَبَّنَا تَقَبَّلۡ مِنَّآۖ إِنَّكَ أَنتَ ٱلسَّمِيعُ ٱلۡعَلِيمُ.

Our Lord, accept [this] from us. Indeed You are the Hearing, the Knowing.

Rabbana taqabbal minna innaka Anta-s-Samiu-l-Alim.

Although Prophets Ibraheem and Isma’eel were carrying out Allah’s command by raising the foundations of the Ka’bah, they were still concerned that Allah might not accept this deed from them. This is a direct result of the humility and humbleness with which they worshipped Allah, and so they supplicated in earnest hope that Allah would accept this magnificent act of worship and that it would bring benefit to nations and generations to come. – Tafseer As-Sa’di.