(How) this is said by way of astonishment (can there be a treaty with Allah and with His messenger for the idolaters save those with whom ye made a treaty at the Inviolable Place of Worship?) after the year of al-Hudaybiyyah, the reference here is to the Banu Kinanah. (So long as they are true to you) in that they honour their treaty, (be true to them) completely. (Lo! Allah loveth those who keep their duty) and abstain from breaking their treaties.