فَليَعبُدوا رَبَّ هٰذَا البَيتِ

Let them worship the Lord of this house.

EXEGESIS

Rabb is one who gradually takes something to its completion^{‎[1]Raghib, p. 336.} or its perfection.^{‎[2]Tahqiq, 4/22.} The term is also commonly used to denote the owner of something,^{‎[3]Ayn, 8/256; Fayyumi, p. 214; Jawhari, 1/130; Maqayis, 2/381.} or one who is in charge of something and manages its affairs.^{‎[4]Fayyumi, p. 214.} Thus, in this surah God would be referring to Himself as the owner of the Kaaba, or one who manages its affairs.

However, since it is understood that the content of this surah is linked to the previous surah (Sūrat al-Fīl), this context suggests that God is identifying Himself as the custodian of the Kaaba as shown by His act of destroying Abrahah and his army of elephants.^{‎[5]Tehrānī, al-Balāgh fī Tafsīr al-Qurʾān bil-Qurʾān, 1/206.}

EXPOSITION

This verse contains the main message of the surah, which is a call to the Quraysh to worship God, the Lord of the Kaaba, due to which they have been granted security, comfort, and a means of livelihood.^{‎[6]Amthal, 20/479; Tabrisi, 10/831.} In other words, God is inviting the Quraysh to worship Him because He is the one who has brought about this solidarity and cohesion amongst them and with others due to the presence of His house in that land.^{‎[7]Mizan, 20/366; Jawādī Āmolī, Tasnīm: See footnotes for URL.} This invitation towards Islam was at a time when the enmity of the Quraysh towards Islam was very intense and posed a serious threat to the safety of the Muslims.^{‎[8]Amthal, 20/479.}

INSIGHTS FROM HADITH

1. It has been narrated from Imam al-Bāqir (a) regarding the Kaaba: ‘God has not created a place on the earth more beloved to Him than it.’^{‎[9]Kafi, 4/239.}
2. Imam al-Ṣādiq (a) has said: ‘Verily God, the blessed and exalted, has [placed] 120 mercies around the Kaaba: sixty for those who circumambulate, forty for those who pray, and twenty for those who look [at the Kaaba].’^{‎[10]Kafi, 4/240.}
3. Imam al-Ṣādiq (a) has said: ‘Whoever looks at the Kaaba, good deeds are continuously written for him and evil deeds are erased from him until he turns his gaze away from it.’^{‎[11]Kafi, 4/240.}
4. It has been narrated from Imam al-Ṣādiq (a): ‘The religion will continue to exist as long as the Kaaba remains standing.’^{‎[12]Kafi, 4/271.}
5. From Imam al-Bāqir: ‘The first place to be created from the earth was [that of] the Kaaba then the [rest of] the earth was extended from it.’^{‎[13]Faqih, 2/241.}

[1] Raghib, p. 336.
[2] Tahqiq, 4/22.
[3] Ayn, 8/256; Fayyumi, p. 214; Jawhari, 1/130; Maqayis, 2/381.
[4] Fayyumi, p. 214.
[5] Tehrānī, al-Balāgh fī Tafsīr al-Qurʾān bil-Qurʾān, 1/206.
[6] Amthal, 20/479; Tabrisi, 10/831.
[7] Mizan, 20/366; Jawādī Āmolī, Tasnīm: 
http://javadi.esra.ir/-/%D8%AA%D9%81%D8%B3%DB%8C%D8%B1-%D8%B3%D9%88%D8%B1%D9%87-%D9%82%D8%B1%DB%8C%D8%B4-1399-01-19.
[8] Amthal, 20/479.
[9] Kafi, 4/239.  
[10] Kafi, 4/240.
[11] Kafi, 4/240.
[12] Kafi, 4/271.
[13] Faqih, 2/241.