Answered by Shaykh Faraz Rabbani
Which would be the better time to begin I`tikaf [spiritual retreat]? At maghrib or at fajr?
Walaikum assalam wa rahmatullah,
If all else is equal, then after maghrib: voluntary worship at night is generally superior to voluntary worship during the day, besides the specific sunna worship.
073.001 O You wrapped up in your raiment!
073.002 Keep vigil the night long, save a little –
073.003 A half thereof, or abate a little thereof
073.004 Or add (a little) thereto – and chant the Quran in measure,
073.005 For we shall charge You with a word of weight.
073.006 Lo! the vigil of the night is (a time) when impression is more keen and speech more certain.
073.007 Lo! You have by day a chain of business.
073.008 So remember the name of your Lord and devote thyself with a complete devotion –
073.009 Lord of the East and the West; there is no God save Him; so choose You Him alone for your defender –
073.010 And bear with patience what they utter, and part from them with a fair leave-taking.