Fasting, whether in Ramadhan or as Nafl is a great act of worship and eating Sehri is an act of merit. Anas Radhi Allah says that our eternally blessed Prophet said “Have Sehri because it brings abundance” (Bukhari)
Abdullah bin Umar has related that our revered and blessed Prophet said:-
“Verily Allah and His angels shower mercy on those who have Sehri” (Targhib ref. Ibn Jaban and Tibrani)
Abu Sa’ad Khidri Radhi Allah relates that our blessed Prophet has said:
“Sehri is (a source of) abundance, so do not leave it even if you take first one mouthful of water, because Allah and His angels shower mercy on sehri-eaters” (Musuad-e-Ahmed and Isnadahu Qavi).
it is better to have Sehri in the last part of the night.
while fasting, one should hurry with iftar after one is sure that the sun has set. Delaying Iftar without any legitimate cause is not allowed. Sahl ibn Saad Radhi Allah Anhu related that our blessed Prophet has said “People shall be on welfare as long as they hurry in Iftar (Bukhari and Muslim).
Abu Hurairah Radhi Allah Anhu has said that our blessed Prophet has said that “Those of His bondsmen are dear to Allah who hurry with Iftar (breaking fast)”. Musnad-e-Ahmed and Tirmidhi).