The phrase “two by two” means that the night prayer is offered in sets of two rakʿahs, each set concluded with the tashahhud and the two salāms; it is performed in pairs, not as a four-rakʿah block.

One should prolong the standing, bowing, and prostration.

It is also preferable to perform the tahajjud in one’s house, for the scholars are unanimous that voluntary prayers are better at home. The Prophet (peace and blessings be upon him) himself prayed in his house and said, “Pray in your houses, for the best prayer a person offers is in his house, except for the prescribed prayers,” recorded by Muslim. Praying at home is also closer to sincerity.

Praying a voluntary prayer while standing is superior to praying it seated without excuse, because the Prophet (peace and blessings be upon him) said, “Whoever prays standing—that is better; and whoever prays seated receives half the reward of the one who prays standing,” agreed upon.

However, if a person prays a voluntary prayer seated due to a legitimate excuse, he receives the same reward as one who prays standing, for the Prophet (peace and blessings be upon him) said, “When a servant becomes ill or travels, there is recorded for him whatever he used to do while resident and healthy.”