That is, We sent Noah with the saying, 'Indeed, I am to you a clear warner.' Its meaning is that We sent him entangled with this saying. It is His words, 'Indeed, I am to you a clear warner,' with a kasrah. When the preposition is attached, it is opened as it is opened in 'as if.' The meaning is based on the kasrah, as in your saying: 'Indeed, Zayd is like the lion.' It has also been recited with a kasrah intending the saying 'not to worship except Allah' as a substitute for 'Indeed, I am to you a clear warner,' meaning We sent him with the command not to worship except Allah. Or 'that' could be an explanation related to 'We sent.' The day is described as painful due to the metaphorical attribution of pain occurring in it. If you say: What if it is described with punishment? I say: It is metaphorical like it, because the painful one in reality is the one who punishes. An example of this is your saying: 'Your day is fasting,' and 'his seriousness is serious.'