"And when My servants ask you concerning Me." The commentary of Qatada: He said: It was mentioned to us that when Allah, blessed and exalted is He, revealed: "Call upon Me; I will respond to you," a man asked: How should we call upon You, O Messenger of Allah? So Allah revealed: "And when My servants ask you concerning Me, indeed I am near."
﴿وَإِذا سَأَلَك عبَادي عني﴾ تَفْسِير قَتَادَة: قَالَ: ذُكِرَ لَنَا أَنَّهُ لما أنزل اللَّه تبارك وتعالى ﴿ادْعُونِي أَسْتَجِب لكم﴾ قَالَ رَجُل: كَيفَ نَدْعُو يَا رَسُول اللَّه؟ فَأنْزل اللَّه: ﴿وَإِذَا سَأَلَكَ عِبَادِي عَنِّي فَإِنِّي قَرِيبٌ﴾