What according to the Prophet will be the heaviest thing that will be put on a believer's scale on the Day of Resurrection? The heaviest thing on the scale is ikhlas, or sincerity. It isn't anything physical or quantitative.  If you offer many units of prayer, perform the pilgrimage many times, observe too many fasts -- all this would not be heavy on the scales.  The more sincere you are, the heavier your balance. Ikhlas means that the qualitative aspect of your deeds is more important. The quantitative aspect of your deeds is of relatively less importance. There are many hadith and verses which tell us that the quantitative aspect is secondary. The qualitative aspect is primary in Islam -- this is what will weigh heavier on the scales.