Pasuram:

ennAL emperumAn undhanakku adiyOm enRu ezhuththuppatta
annALE adiyOngkaL adikkudil vIdu peRRu uyndhadhu kAN
sennAL thORRith thirumadhuraiyuL silai kuniththu ainthalaiya
painnAgaththalaip pAyndhavanE! unnaip pallANdu kURudhumE

Meaning:

emperumAn 			- Our Lord!
ennAL 				- whichever day
ezhuththuppatta 		- we gave in writing
adiyOm enRu 			- that we are in Your service
un thanakku 			- to You (who is Supreme),
annALE 				- on that day itself
kudil 				- the household (including our children and grandchildren)
adiyOngkaL 			- of we who are in Your service
adi 				- became Your servants,
vIdu peRRu 			- and escaping from kaivalya
uyndhadhu 			- attained upliftment.
thORRi 				- Descended (Born)
sem nAL 			- in the beautiful divine day
thiru madhuraiyuL 		- in the divine Mathura city,
silai kuniththu			- and (in Kamsa's weaponry) bent and broke the bow,
pAyndhavanE 			- the Lord who jumped on
thalai 				- on the head
nAgam 				- of the snake Kaliya
ainthaliya 			- with its five heads
pai 				- and hoods; 
unnai 				- to You
pallANdu kURudhum 		- we perform mangalashasanam.

Vyakhyana Saram:
In the previous pasuram, those who seek nothing but Him, spoke of the fact that even in this world (with their physical bodies) their nature is one of subservience to Him and joined Azhvar in singing His praises.

In this pasuram, those who sought things other than Him are joining Azhvar. Since they don't have the greatness of the other group, they speak of what they gained due to His prowess and join Azhvar. It was in this way that when those who sought material wealth joined Azhvar, they said "sAnthamum thandhu ennai veLLuiyir Akka valla". They had expressed their amazement at His divine mercy in His giving them the lowly things that they sought and through that changing their nature to a pure one.

For those who sought kaivalya, had He given them that, it would have meant eternal destruction. They are therefore celebrating in this pasuram, His mercy in rescuing them at the time when they asked for kaivalya.