Sujud is the adornment of prayer. So, perform it properly. Imam Sadiq (A.S) says: “Whenever you perform prayer, perform the ruku and sujud well as God will give seventy times the reward or even more.”‌[1]
Sujud is the source of pride of God to the angels, and thus, it entails His favor such that in every sujud, one of man’s sins is forgiven and a great reward is recorded for him.[2] Hazrat Ali (A.S) said: “If man only knew what mercy envelopes him at the time of sujud, he would never raise up his head from that state.”‌[3]
Sujud extinguishes the spirit of egoism and pride, and delivers man from vanity. [4]
The Prophet (PBUH) used to say: “On the Day of Resurrection, I will identify my ummah by the mark of prostration that they have on their foreheads.”‌[5] That portion of the earth on which prostration was made will testify to the devotion of man on the Day of Resurrection[6] and even in the world, a radiant point connect it to the heavens.[7]
As in the case of ruku‘, long prostrations result in the permanence of favors and longevity. [8]
Sujud is so important that God commands a great Prophet (PBUH) such as Ibrahim (Abraham) (PBUH), to cleanse Masjid al-Haram for those who perform the circumambulation [Tawaf] of the Kaba, ruku and sujud.[9]
The wisdom behind sujud
The Commander of the Faithful Imam Ali (A.S) was asked concerning the wisdom behind sujud. The Imam (A.S) said: “The first sujud means that I was dust in the beginning, and as I raise my head from sujud, it means that I came to the world from the dust. The second sujud means that I will again return to the soil, and as I raise my head from sujud, it means that on the Day of Resurrection I will rise up from the grave and be summoned.”‌[10]
Imam Sadiq (A.S) says: “Since sujud is for God, it must therefore not be done on anything that is eaten or worn which draws the attention of materialists. Sujud must remind man of God, not the stomach, clothing and material things.”‌[11]
We read in the hadith that the reason behind the prostration for forgetfulness [sujud sahwi] for unintentional excess and deficiencies (in the number of any essential pillar of the prayer) or misplaced utterance, standing and sitting is that Iblis distracted your attention and created disorder in your prayer. Therefore, after prayer you perform two prostrations so as to rub his nose in the ground and to inform him that every time he creates disorder, you will again perform prostration before God. [12]
Hazrat Ali (A.S) said: “The external appearance [zahir] of the sujud is the placing of the forehead on the ground with sincerity and humility, but its esoteric essence [bat‌in] is the detachment of the heart from all perishable things, attachment of the heart to the eternal abode, and relief from pride, fanaticism and all worldly attachments.[13]

Footnotes:
[1] Bihar al-Anwar, vol. 85, p. 139.
[2] Jami‘ al-Ahadith, vol. 5, p. 466.
[3] Jami‘ al-Ahadith, vol. 5, p. 482.
[4] Jami‘ al-al-Ahadith, vol. 5, p. 453.
[5] Musnad Ahmad ibn Hanbal, vol. 4, p. 189.
[6] Jami‘ al-Ahadith, vol. 5, p. 189.
[7] Mustadrak al-Wasaiil, vol. 4, p. 485.
[8] Wasa’il ash-Shi‘ah, vol. 4, p. 928.
[9] Surah al-Baqarah 2:125: “We charged Abraham and Ishmael [with its upkeep, saying], ‘Purify My House for those who go around it, for those who make it a retreat and for those who bow and prostrate.”‌
[10] Bihar al-Anwar, vol. 85, p. 139.
[11] Al-Faqih, vol. 1, p. 282.
[12] Al-Wafi, vol. 8, p. 992.
[13] Mustadrak al-Wasail, vol. 4, p. 484.