Hawzah News Agency – Imam al-Jawad (AS), when asked about death said:

هُو النَّومُ الّذي يأتيكُم كُلَّ ليلَةٍ إلّا أنّهُ طويلٌ مُدَّتُهُ لا يُنتَبَهُ مِنهُ إلّا يَومَ القيامَةِ، فمَن رأى‏ في نَومِهِ من أصنافِ الفَرَحِ ما لا يُقادِرُ قَدرَهُ، ومِن أصنافِ الأهوالِ ما لا يُقادِرُ قَدرَهُ، فكيفَ حالُ فَرِحٍ في النَّومِ ووَجِلٍ فيهِ؟ هذا هُو المَوتُ، فاستَعِدُّوا لَهُ.

'It is the sleep that comes to you every night, however its period is long and none will wake from it until the Day of Resurrection. So he who sees in his sleep different kinds of happy states whose extent he cannot fathom and different kinds of terrors he cannot fathom, then how does the happy and the dismayed feel in death? This is death so prepare for it.'

Source: Maani al-Akhbar, p. 289, no. 5