The Quran

قُل لِعِبادِيَ الَّذينَ آمَنوا يُقيمُوا الصَّلاةَ وَيُنفِقوا مِمّا رَزَقناهُم سِرًّا وَعَلانِيَةً مِن قَبلِ أَن يَأتِيَ يَومٌ لا بَيعٌ فيهِ وَلا خِلالٌ

Muhammad Asad

[And] tell [those of] My servants who have attained to faith that they should be constant in prayer and spend [in Our way], secretly and openly, out of what We provide for them as sustenance,¹ ere there come a Day when there will be no bargaining, and no mutual befriending.²

See surah 2, note 4.
Cf. 2:254. According to the philologist Abu 'Ubaydah, as quoted by Razi, the expression bay' ("selling and buying" or "bargaining") denotes here the metaphorical "[giving and taking] ransom" which, as the Qur'an repeatedly stresses, will be inadmissible on the Day of Judgment (cf. 3:91 and the corresponding note 71, as well as 5:36, 10: 54, 13:18, 39:47 and 70:11-15); similarly, the denial of khildl - which Abu 'Ubaydah regards as synonymous, in this context, with mukhalah ("mutual befriending")- expresses the impossibility of "ransom" through intercession on Judgment Day, for "now, indeed, you have come unto Us in a lonely state, even as We created you in the first instance" (6:94).