One important objection against accepting the authenticity of the Syriac Sermon on Palm Sunday as being from the hand of Ephrem the Syrian, is the use of explicit Trinitarian language in lines 426-431 of the sermon. This section of text forms part of the unit that consists of lines 418-447 in which Israel is criticized for rejecting their 'King' in the desert (at Sinai), and the Jewish contemporaries of Jesus are criticized for rejecting 'the Son of the King' in Jerusalem. A close reading of these lines suggests that the part where the Holy Spirit and the Trinity are mentioned might constitute a later, 'more orthodox' interpolation into the original text. These lines disturb the original parallel and clash with the poetic quality of the original. The article considers the possibility that the sermon, without this interpolation, might after all have been written by Ephrem himself.