Word-by-word:
sāvatthiyaṃ in Savatthi tadā then vasanti. were dwelling satta seven manussakoṭiyo koti of humans tesu of them pañcakoṭimattā a total of five koti manussā humans sutvā having heard dhammakathaṃ a dhamma talk satthu of the teacher jātā, had become ariyasāvakā noble disciples dvekoṭimattā a total of two koti manussā humans puthujjanā. [were] defiled beings. tesu of them, ahesuṃ there were dveyeva just two kiccāni duties ariyasāvakānaṃ of the noble disciples purebhattaṃ before the meal denti, they give dānaṃ charity pacchābhattaṃ after the meal gandhamālādihatthā with hands full of scents, garlands, etc. gāhāpetvā having ordered the bringing of vatthabhesajjapānakādīni cloth, medicines, drinks, etc. gacchanti. would go dhammassavanatthāya for the purpose of listening to the dhamma. athekadivasaṃ then, one day, mahāpālo Mahapaala disvā having seen ariyasāvake the noble disciples gandhamālādihatthe with hands full of scents, garlands, etc. gacchante going to vihāraṃ the monastery pucchitvā having asked, iti thus: kuhiṃ "to where ayaṃ [is] this mahājano great crowd gacchati going?" sutvā having heard, iti thus: “dhammassavanāya” "for listening to the dhamma" iti [thought] thus: “ahampi "I, too, gamissāmi” will go." gantvā having gone, vanditvā having paid homage satthāraṃ to the teacher, nisīdi. sat parisapariyante at the perimeter of the assembly.
Proper:
In Savatthi, just then, were dwelling seven koti of people. Of them, a total of five koti of people, having heard talk on the dhamma from the teacher, had become noble disciples. A total of two koti humans were still fully-defiled beings.
Of them, two duties were undertaken only by the noble disciples:
1) before the meal they would give charity;
2) after the meal, with hands full of scents, garlands, etc. having ordered the bringing of cloth, medicines, drinks, etc. they would go for the purpose of listening to the dhamma.
Then, one day, Mahapaala having seen the noble disciples with hands full of scents, garlands, etc. going to the monastery, asked, "to where [is] this great crowd going?" Having heard, "for listening to the dhamma", he thought, "I, too, will go." Having gone and paid homage to the teacher, he sat at the perimeter of the gathering.