Lacrymosa

Lacrymosa dies illa,

qua resurget ex favilla judicandus homo reus.

Lacrymosa dies illa,

qua resurget ex favilla judicandus homo reus.
Huic ergo parce Deus, pie Jesu.

Jesu Domine.

Dona eis requiem! Amen!

Tearful that day,
on which will rise from ashes
guilty man for judgment.
So have mercy, O Lord, on this man.
Compassionate Lord Jesus,
grant them rest. Amen.

The eccentric count Franz von Walsegg commissioned the Requiem from Mozart anonymously through intermediaries acting on his behalf. The count, an amateur chamber musician who routinely commissioned works by composers and passed them off as his own, wanted a Requiem mass he could claim he composed to memorialize the recent passing of his wife. Mozart received only half of the payment in advance, so upon his death his widow Constanze was keen to have the work completed secretly by someone else, submit it to the count as having been completed by Mozart and collect the final payment. Joseph von Eybler was one of the first composers to be asked to complete the score, and had worked on the movements from the Dies irae up until the Lacrimosa. In addition, a striking similarity between the openings of the Domine Jesu Christe movements in the requiems of the two composers suggests that Eybler at least looked at later sections. Following this work, he felt unable to complete the remainder, and gave the manuscript back to Constanze Mozart.
The task was then given to another composer, Franz Xaver Süssmayr, who had already helped the ailing Mozart in writing the score, since in his final days the composer's limbs had become extremely swollen. Süssmayr borrowed some of Eybler's work in making his completion, and added his own orchestration to the movements from the Dies Irae onward (the Kyrie was orchestrated before either Süssmayr or Eybler began their work), completed the Lacrimosa, and added several new movements which a Requiem would normally comprise: Sanctus, Benedictus, and Agnus Dei. He then added a final section, Lux aeterna by adapting the opening two movements which Mozart had written to the different words which finish the Requiem Mass, which according to both Süssmayr and Mozart's wife was done according to Mozart's directions. Whether or not that is true, some people consider it unlikely that Mozart would have repeated the opening two sections if he had survived to finish the work completely. However, the fact that the work ends with a recapitulation of the first movement creates a work which, overall, displays characteristics of sonata form, which may help to authenticate the idea for the repetition of the first movement as the final movement. As has often been stated, Mozart was not the only composer to do this, and many requiems written before his repeat the first movement as the last. (In regular Masses a similar practice existed where the last movement, the Agnus Dei, was indicated only by the words "ut Kyrie", "as the Kyrie".)