SB 4.13.31

sadasas-pataya ūcuḥ
nara-deveha bhavato
 nāghaṁ tāvan manāk sthitam
asty ekaṁ prāktanam aghaṁ
 yad ihedṛk tvam aprajaḥ
Synonyms: 
sadasaḥ-patayaḥ ūcuḥ — the head priests said; nara-deva — O King; iha — in this life; bhavataḥ — of you; na — not; agham — sinful activity; tāvat manāk — even very slight; sthitam — situated; asti — there is; ekam — one; prāktanam — in the previous birth; agham — sinful activity; yat — by which; iha — in this life; īdṛk — like this; tvam — you; aprajaḥ — without any son.
Translation: 
The head priests said: O King, in this life we do not find any sinful activity, even within your mind, so you are not in the least offensive. But we can see that in your previous life you performed sinful activities due to which, in spite of your having all qualifications, you have no son.
Purport: 

The purpose of marrying is to beget a son, because a son is necessary to deliver his father and forefathers from any hellish conditional life in which they may be. Cāṇakya Paṇḍita therefore says, putra-hīnaṁ gṛhaṁ śūnyam: without a son, married life is simply abominable. King Aṅga was a very pious king in this life, but because of his previous sinful activity he could not get a son. It is concluded, therefore, that if a person does not get a son it is due to his past sinful life.