Musnad Ahmad Hadith 21603

It is narrated from Zaid bin Thabit (may Allah be pleased with him) that once the Holy Prophet (ﷺ) made a tent out of a mat in the mosque and prayed in it for several nights, until people also began to gather. After a few days, the voice of the Holy Prophet (ﷺ) was not heard, so people thought that perhaps the Holy Prophet (ﷺ) had fallen asleep. Therefore, some people went near and started coughing so that the Holy Prophet (ﷺ) would come out. The Holy Prophet (ﷺ) said, "I was continuously observing your action until I feared that this prayer (Tahajjud) might become obligatory upon you, because if this prayer becomes obligatory upon you, you will not be able to adhere to it. Therefore, O people! Pray in your homes, for apart from the obligatory prayers, praying other prayers at home is the best for a person."